IB/hfi1: Harden state transition to Armed and Active

There is a window that allows other threads to read state of
'host_link_state' as a new, before the hardware actual state is set.
This patch closes the window by indicating a new state only after
hardware transition is complete.

Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Alex Estrin <alex.estrin@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>