nvme_trans_modesel_get_mp() was defined with a unsigned return
type, but can return signed values.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NVishal Verma <vishal.l.verma@linux.intel.com>
Signed-off-by: NMatthew Wilcox <matthew.r.wilcox@intel.com>