Replace function with macro that already exists

I wrote a function to determine the base algorithm given a variant,
however this is already implemented by
PSA_ALG_AEAD_WITH_DEFAULT_LENGTH_TAG

Signed-off-by: Paul Elliott <paul.elliott@arm.com>
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index aec22c7..9254f36 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -3398,20 +3398,7 @@
 /* Helper function to get the base algorithm from its variants. */
 static psa_algorithm_t psa_aead_get_base_algorithm(psa_algorithm_t alg)
 {
-    switch( PSA_ALG_AEAD_WITH_SHORTENED_TAG( alg, 0 ) )
-    {
-        case PSA_ALG_AEAD_WITH_SHORTENED_TAG( PSA_ALG_CCM, 0 ):
-            return( PSA_ALG_CCM );
-
-        case PSA_ALG_AEAD_WITH_SHORTENED_TAG( PSA_ALG_GCM, 0 ):
-            return( PSA_ALG_GCM );
-
-        case PSA_ALG_AEAD_WITH_SHORTENED_TAG( PSA_ALG_CHACHA20_POLY1305, 0 ):
-            return( PSA_ALG_CHACHA20_POLY1305 );
-
-        default:
-            return( PSA_ERROR_NOT_SUPPORTED );
-    }
+    return PSA_ALG_AEAD_WITH_DEFAULT_LENGTH_TAG( alg );
 }
 
 /* Set the key for a multipart authenticated encryption operation. */