net: ethernet: bnx2: Replace NULL comparison

This patch fixes the checkpatch issue of NULL comparison. Replace x == NULL
with !x, by using the following coccinelle script:

@disable is_null@
expression e;
@@
-e==NULL
+!e

Signed-off-by: Varsha Rao <rvarsha016@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>