Rename plain c option and update comments

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/aesni.h b/library/aesni.h
index dddbf99..c17b613 100644
--- a/library/aesni.h
+++ b/library/aesni.h
@@ -39,7 +39,7 @@
     (defined(__amd64__) || defined(__x86_64__))   &&  \
     !defined(MBEDTLS_HAVE_X86_64)
 #define MBEDTLS_HAVE_X86_64
-#if !defined(MBEDTLS_AESNI_C) && defined(MBEDTLS_AES_DONT_USE_SOFTWARE_CRYPTO)
+#if !defined(MBEDTLS_AESNI_C) && defined(MBEDTLS_AES_USE_HARDWARE_ONLY)
 #error "MBEDTLS_AES_C defined, but not all prerequisites"
 #endif
 #endif
@@ -91,7 +91,7 @@
  *
  * \return         1 if CPU has support for the feature, 0 otherwise
  */
-#if !defined(MBEDTLS_AES_DONT_USE_SOFTWARE_CRYPTO)
+#if !defined(MBEDTLS_AES_USE_HARDWARE_ONLY)
 int mbedtls_aesni_has_support(unsigned int what);
 #else
 #define /* no-check-names */ mbedtls_aesni_has_support(what) 1