be2net: Fix a bug in Rx buffer posting

The numPosted field in the ERX Doorbell register is 8-bits wide.
So the max buffers that we can post at a time is 255 and not 256
which we are doing currently.

Signed-off-by: Ajit Khaparde <ajit.khaparde@emulex.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/emulex/benet/be.h

@@ -97,6 +97,7 @@
 #define BE_NAPI_WEIGHT		64
 #define MAX_RX_POST		BE_NAPI_WEIGHT /* Frags posted at a time */
 #define RX_FRAGS_REFILL_WM	(RX_Q_LEN - MAX_RX_POST)
+#define MAX_NUM_POST_ERX_DB	255u
 
 #define MAX_VFS			30 /* Max VFs supported by BE3 FW */
 #define FW_VER_LEN		32