qlcnic: set mtu lower limit

Setting mtu < 68 is not supported.

Signed-off-by: Sritej Velaga <sritej.velaga@qlogic.com>
Signed-off-by: Amit Kumar Salecha <amit.salecha@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/qlcnic/qlcnic.h b/drivers/net/qlcnic/qlcnic.h
index 9d80171..42a2883 100644
--- a/drivers/net/qlcnic/qlcnic.h
+++ b/drivers/net/qlcnic/qlcnic.h
@@ -95,6 +95,7 @@
 #define FIRST_PAGE_GROUP_END	0x100000
 
 #define P3_MAX_MTU                     (9600)
+#define P3_MIN_MTU                     (68)
 #define QLCNIC_MAX_ETHERHDR                32 /* This contains some padding */
 
 #define QLCNIC_P3_RX_BUF_MAX_LEN         (QLCNIC_MAX_ETHERHDR + ETH_DATA_LEN)