bnx2: 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>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bnx2.c

@@ -50,7 +50,7 @@
 #include <linux/log2.h>
 #include <linux/aer.h>
 
-#if defined(CONFIG_CNIC) || defined(CONFIG_CNIC_MODULE)
+#if IS_ENABLED(CONFIG_CNIC)
 #define BCM_CNIC 1
 #include "cnic_if.h"
 #endif