Remove USE_PSA references from X509 documentation

MBEDTLS_USE_PSA_CRYPTO is now always enabled we need to update the
documentation accordingly.

Signed-off-by: Janos Follath <janos.follath@arm.com>
diff --git a/include/mbedtls/x509_csr.h b/include/mbedtls/x509_csr.h
index 8c31c09..08e585f 100644
--- a/include/mbedtls/x509_csr.h
+++ b/include/mbedtls/x509_csr.h
@@ -79,9 +79,8 @@
  *                 ignored, unless the critical flag is set, in which case
  *                 the CSR is rejected.
  *
- * \note           If #MBEDTLS_USE_PSA_CRYPTO is enabled, the PSA crypto
- *                 subsystem must have been initialized by calling
- *                 psa_crypto_init() before calling this function.
+ * \note           The PSA crypto subsystem must have been initialized by
+ *                 calling psa_crypto_init() before calling this function.
  *
  * \param csr      CSR context to fill
  * \param buf      buffer holding the CRL data
@@ -135,9 +134,8 @@
  *                 the result of the callback function decides whether
  *                 CSR is rejected.
  *
- * \note           If #MBEDTLS_USE_PSA_CRYPTO is enabled, the PSA crypto
- *                 subsystem must have been initialized by calling
- *                 psa_crypto_init() before calling this function.
+ * \note           The PSA crypto subsystem must have been initialized by
+ *                 calling psa_crypto_init() before calling this function.
  *
  * \param csr      CSR context to fill
  * \param buf      buffer holding the CRL data
@@ -158,9 +156,8 @@
  *
  * \note           See notes for \c mbedtls_x509_csr_parse_der()
  *
- * \note           If #MBEDTLS_USE_PSA_CRYPTO is enabled, the PSA crypto
- *                 subsystem must have been initialized by calling
- *                 psa_crypto_init() before calling this function.
+ * \note           The PSA crypto subsystem must have been initialized by
+ *                 calling psa_crypto_init() before calling this function.
  *
  * \param csr      CSR context to fill
  * \param buf      buffer holding the CRL data