plat/arm/css/sgi: Fix assert expression issue

Violation of MISRA-C Rule 14.4
Signed-off-by: Ming Huang <huangming@linux.alibaba.com>
Change-Id: I44ef50dadb54fb056a91f3de962b6e63ba6d7ac4

plat/arm/css/sgi/sgi_ras.c

@@ -121,7 +121,7 @@ static int sgi_ras_intr_handler(const struct err_record_info *err_rec,
 	 * this interrupt
 	 */
 	ras_map = find_ras_event_map_by_intr(intr);
-	assert(ras_map);
+	assert(ras_map != NULL);
 
 	/*
 	 * Populate the MM_COMMUNICATE payload to share the