RDMA/nes: Mitigate compatibility issue regarding PCIe write credits

Under heavy load, there is an compatibility issue regarding PCIe write
credits with certain chipsets.  It can be mitigated by limiting read
requests to 256 Bytes.

This workaround is always enabled for Tbird2 on Gladius.  We also add
a module parameter to enable workaround for non-Gladius cards.

Signed-off-by: Chien Tung <chien.tin.tung@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/nes/nes_hw.h

@@ -40,6 +40,7 @@
 #define NES_PHY_TYPE_ARGUS     4
 #define NES_PHY_TYPE_PUMA_1G   5
 #define NES_PHY_TYPE_PUMA_10G  6
+#define NES_PHY_TYPE_GLADIUS   7
 
 #define NES_MULTICAST_PF_MAX 8