IB/hfi1: convert to debugfs_file_get() and -put()

Convert all calls to the now obsolete debugfs_use_file_start() and
debugfs_use_file_finish() to the new debugfs_file_get() and
debugfs_file_put() API.

Fixes: 49d200de ("debugfs: prevent access to removed files' private data")
Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>