IB/hfi1: Fix checks for Offline transient state

In goto_offline() function pstate is masked by 0xff when compared
to PLS_OFFLINE state. Mask should be 0xf0, since upper 4 bits
specify the "major" state.

Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Reviewed-by: Easwar Hariharan <easwar.hariharan@intel.com>
Signed-off-by: Jakub Byczkowski <jakub.byczkowski@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>