MIPS: bitops.h: Change use of 'unsigned short' to 'int'

[ralf@linux-mips.org: No functional change but it's consistent with how
use types elsewhere in the code.]

Signed-off-by: Jim Quinlan <jim2101024@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: David Daney <ddaney.cavm@gmail.com>
Cc: Kevin Cernekee cernekee@gmail.com
Cc: Jim Quinlan <jim2101024@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/4319/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>