Fix some errors in PSA_ASYMMETRIC_DECRYPT_OUTPUT_SIZE

A call to PSA_ASYMMETRIC_DECRYPT_OUTPUT_SIZE wouldn't even have
compiled. Fix some obvious errors. This is still untested.
diff --git a/include/psa/crypto.h b/include/psa/crypto.h
index c0b3187..0840494 100755
--- a/include/psa/crypto.h
+++ b/include/psa/crypto.h
@@ -1368,11 +1368,13 @@
     (PSA_KEY_TYPE_IS_RSA(key_type) ?                                    \
      ((void)alg, PSA_BITS_TO_BYTES(key_bits)) :                         \
      0)
-#define PSA_ASYMMETRIC_DECRYPT_OUTPUT_SIZE(key_type, key_bits, alg) \
+#define PSA_RSA_MINIMUM_PADDING_SIZE(alg)                               \
+    (PSA_ALG_IS_RSA_OAEP_MGF1(alg) ?                                    \
+     2 * PSA_HASH_FINAL_SIZE(PSA_ALG_RSA_GET_HASH(alg)) + 1 :           \
+     11 /*PKCS#1v1.5*/)
+#define PSA_ASYMMETRIC_DECRYPT_OUTPUT_SIZE(key_type, key_bits, alg)     \
     (PSA_KEY_TYPE_IS_RSA(key_type) ?                                    \
-     PSA_BITS_TO_BYTES(key_bits) - ((alg) == PSA_ALG_IS_RSA_OAEP_MGF1 ? \
-                                    2 * (PSA_ALG_RSA_GET_HASH(alg) + 1) : \
-                                    11 /*PKCS#1v1.5*/) :                \
+     PSA_BITS_TO_BYTES(key_bits) - PSA_RSA_MINIMUM_PADDING_SIZE(alg) :  \
      0)
 
 /**