qed: Add sanity check for SIMD fastpath handler.

Avoid calling a SIMD fastpath handler if it is NULL. The check is needed
to handle an unlikely scenario where unsolicited interrupt is destined to
a PF in INTa mode.

Fixes: fe56b9e6 ("qed: Add module with basic common support")
Signed-off-by: Sudarsana Reddy Kalluru <Sudarsana.Kalluru@cavium.com>
Signed-off-by: Ariel Elior <ariel.elior@cavium.com>
Signed-off-by: Michal Kalderon <Michal.Kalderon@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/qlogic/qed/qed_main.c

@@ -567,8 +567,16 @@ static irqreturn_t qed_single_int(int irq, void *dev_instance)
 		/* Fastpath interrupts */
 		for (j = 0; j < 64; j++) {
 			if ((0x2ULL << j) & status) {
-				hwfn->simd_proto_handler[j].func(
-					hwfn->simd_proto_handler[j].token);
+				struct qed_simd_fp_handler *p_handler =
+					&hwfn->simd_proto_handler[j];
+
+				if (p_handler->func)
+					p_handler->func(p_handler->token);
+				else
+					DP_NOTICE(hwfn,
+						  "Not calling fastpath handler as it is NULL [handler #%d, status 0x%llx]\n",
+						  j, status);
+
 				status &= ~(0x2ULL << j);
 				rc = IRQ_HANDLED;
 			}