bnx2x: limit number of interrupt vectors for 57711

Original straightforward division may lead to zeroing number of SB and
null-pointer dereference when device is short of MSIX vectors or lacks
MSIX capabilities.

Reported-by: Vladislav Zolotarov <vladz@cloudius-systems.com>
Signed-off-by: Dmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: Yuval Mintz <yuvalmin@broadcom.com>
Signed-off-by: Ariel Elior <ariele@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bnx2x/bnx2x.h

@@ -2499,4 +2499,6 @@ void bnx2x_set_local_cmng(struct bnx2x *bp);
 #define MCPR_SCRATCH_BASE(bp) \
 	(CHIP_IS_E1x(bp) ? MCP_REG_MCPR_SCRATCH : MCP_A_REG_MCPR_SCRATCH)
 
+#define E1H_MAX_MF_SB_COUNT (HC_SB_MAX_SB_E1X/(E1HVN_MAX * PORT_MAX))
+
 #endif /* bnx2x.h */

drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c

@@ -11447,9 +11447,9 @@ static int bnx2x_get_hwinfo(struct bnx2x *bp)
 		}
 	}
 
-	/* adjust igu_sb_cnt to MF for E1x */
-	if (CHIP_IS_E1x(bp) && IS_MF(bp))
-		bp->igu_sb_cnt /= E1HVN_MAX;
+	/* adjust igu_sb_cnt to MF for E1H */
+	if (CHIP_IS_E1H(bp) && IS_MF(bp))
+		bp->igu_sb_cnt = min_t(u8, bp->igu_sb_cnt, E1H_MAX_MF_SB_COUNT);
 
 	/* port info */
 	bnx2x_get_port_hwinfo(bp);