IB/hfi1: Fix serdes loopback set-up

Change serdes mode setting to use MISC_CONFIG_BITS in
VERIFY_CAP_LOCAL_LINK_WIDTH register. This method of
setting up serdes loopback is universally compatible
across all firmware versions.

Reviewed-by: Jakub Byczkowski <jakub.byczkowski@intel.com>
Signed-off-by: Jan Sokolowski <jan.sokolowski@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/hfi1/chip.h

@@ -582,6 +582,9 @@ enum {
 #define LOOPBACK_LCB	2
 #define LOOPBACK_CABLE	3	/* external cable */
 
+/* set up serdes bit in MISC_CONFIG_BITS */
+#define LOOPBACK_SERDES_CONFIG_BIT_MASK_SHIFT 0
+
 /* read and write hardware registers */
 u64 read_csr(const struct hfi1_devdata *dd, u32 offset);
 void write_csr(const struct hfi1_devdata *dd, u32 offset, u64 value);