Remove redundant key_set from MAC operation structure

The purpose of key_set was to guard the operation structure from being
used for update/finish before a key was set. Now that the implementation
fully adheres to the PSA API, that function is covered by the `alg`
variable instead. It's set to the algorithm in use when a key is set, and
is zero when the operation is reset/invalid.

Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
diff --git a/include/psa/crypto_builtin_composites.h b/include/psa/crypto_builtin_composites.h
index 3b0f82a..780a6c5 100644
--- a/include/psa/crypto_builtin_composites.h
+++ b/include/psa/crypto_builtin_composites.h
@@ -62,7 +62,6 @@
 typedef struct
 {
     psa_algorithm_t alg;
-    unsigned int key_set : 1;
     unsigned int has_input : 1;
     unsigned int is_sign : 1;
     uint8_t mac_size;
@@ -78,7 +77,7 @@
     } ctx;
 } mbedtls_psa_mac_operation_t;
 
-#define MBEDTLS_PSA_MAC_OPERATION_INIT {0, 0, 0, 0, 0, {0}}
+#define MBEDTLS_PSA_MAC_OPERATION_INIT {0, 0, 0, 0, {0}}
 
 /*
  * BEYOND THIS POINT, TEST DRIVER DECLARATIONS ONLY.