Change contract of MD<->PSA conversion

This is preparation work for simplifying the implementation of those
functions. Done first in order to get the CI's opinion on it.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/library/md.c b/library/md.c
index ac06198..932c6d0 100644
--- a/library/md.c
+++ b/library/md.c
@@ -774,34 +774,20 @@
 psa_algorithm_t mbedtls_md_psa_alg_from_type(mbedtls_md_type_t md_type)
 {
     switch (md_type) {
-#if defined(MBEDTLS_MD_CAN_MD5)
         case MBEDTLS_MD_MD5:
             return PSA_ALG_MD5;
-#endif
-#if defined(MBEDTLS_MD_CAN_RIPEMD160)
         case MBEDTLS_MD_RIPEMD160:
             return PSA_ALG_RIPEMD160;
-#endif
-#if defined(MBEDTLS_MD_CAN_SHA1)
         case MBEDTLS_MD_SHA1:
             return PSA_ALG_SHA_1;
-#endif
-#if defined(MBEDTLS_MD_CAN_SHA224)
         case MBEDTLS_MD_SHA224:
             return PSA_ALG_SHA_224;
-#endif
-#if defined(MBEDTLS_MD_CAN_SHA256)
         case MBEDTLS_MD_SHA256:
             return PSA_ALG_SHA_256;
-#endif
-#if defined(MBEDTLS_MD_CAN_SHA384)
         case MBEDTLS_MD_SHA384:
             return PSA_ALG_SHA_384;
-#endif
-#if defined(MBEDTLS_MD_CAN_SHA512)
         case MBEDTLS_MD_SHA512:
             return PSA_ALG_SHA_512;
-#endif
         default:
             return PSA_ALG_NONE;
     }
@@ -810,34 +796,20 @@
 mbedtls_md_type_t mbedtls_md_type_from_psa_alg(psa_algorithm_t psa_alg)
 {
     switch (psa_alg) {
-#if defined(MBEDTLS_MD_CAN_MD5)
         case PSA_ALG_MD5:
             return MBEDTLS_MD_MD5;
-#endif
-#if defined(MBEDTLS_MD_CAN_RIPEMD160)
         case PSA_ALG_RIPEMD160:
             return MBEDTLS_MD_RIPEMD160;
-#endif
-#if defined(MBEDTLS_MD_CAN_SHA1)
         case PSA_ALG_SHA_1:
             return MBEDTLS_MD_SHA1;
-#endif
-#if defined(MBEDTLS_MD_CAN_SHA224)
         case PSA_ALG_SHA_224:
             return MBEDTLS_MD_SHA224;
-#endif
-#if defined(MBEDTLS_MD_CAN_SHA256)
         case PSA_ALG_SHA_256:
             return MBEDTLS_MD_SHA256;
-#endif
-#if defined(MBEDTLS_MD_CAN_SHA384)
         case PSA_ALG_SHA_384:
             return MBEDTLS_MD_SHA384;
-#endif
-#if defined(MBEDTLS_MD_CAN_SHA512)
         case PSA_ALG_SHA_512:
             return MBEDTLS_MD_SHA512;
-#endif
         default:
             return MBEDTLS_MD_NONE;
     }
diff --git a/library/md_psa.h b/library/md_psa.h
index 6645c83..3231a60 100644
--- a/library/md_psa.h
+++ b/library/md_psa.h
@@ -33,8 +33,8 @@
  *
  * \param md_type   The type of digest to search for.
  *
- * \return          The PSA algorithm identifier associated with \p md_type.
- * \return          PSA_ALG_NONE if the algorithm is not supported.
+ * \return          The PSA algorithm identifier associated with \p md_type,
+ *                  regardless of whether it is supported or not.
  */
 psa_algorithm_t mbedtls_md_psa_alg_from_type(mbedtls_md_type_t md_type);
 
@@ -44,8 +44,8 @@
  *
  * \param psa_alg   The PSA algorithm identifier to search for.
  *
- * \return          The MD type associated with \p psa_alg.
- * \return          MBEDTLS_MD_NONE if the algorithm is not supported.
+ * \return          The MD type associated with \p psa_alg,
+ *                  regardless of whether it is supported or not.
  */
 mbedtls_md_type_t mbedtls_md_type_from_psa_alg(psa_algorithm_t psa_alg);