IB/hfi1: Correct external device configuration shift

The external device configuration was incorrectly shifted to byte 3 of
the 32 bit DC_HOST_COMM_SETTINGS instead of byte 0. This patch corrects
the shift and provides the cable capability information in byte 0.

Reviewed-by: Dean Luick <dean.luick@intel.com>
Signed-off-by: Easwar Hariharan <easwar.hariharan@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>