uapi/hfi1_user: Add command and event for TID caching

TID caching will use a new event to signal userland that cache
invalidation has occurred and needs a matching command code that
will be used to read the invalidated TIDs.

Add the event bit and the new command to the exported header file.

The command is also added to the switch() statement in file_ops.c
for completeness and in preparation for its usage later.

Signed-off-by: Mitko Haralanov <mitko.haralanov@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>