sctp: use IS_ENABLED() instead of checking for built-in or module

The IS_ENABLED() macro checks if a Kconfig symbol has been enabled either
built-in or as a module, use that macro instead of open coding the same.

Using the macro makes the code more readable by helping abstract away some
of the Kconfig built-in and module enable details.
Signed-off-by: NJavier Martinez Canillas <javier@osg.samsung.com>
Acked-by: NNeil Horman <nhorman@tuxdriver.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sctp/auth.c

@@ -48,7 +48,7 @@ static struct sctp_hmac sctp_hmac_list[SCTP_AUTH_NUM_HMACS] = {
 		/* id 2 is reserved as well */
 		.hmac_id = SCTP_AUTH_HMAC_ID_RESERVED_2,
 	},
-#if defined (CONFIG_CRYPTO_SHA256) || defined (CONFIG_CRYPTO_SHA256_MODULE)
+#if IS_ENABLED(CONFIG_CRYPTO_SHA256)
 	{
 		.hmac_id = SCTP_AUTH_HMAC_ID_SHA256,
 		.hmac_name = "hmac(sha256)",