MIPS: Sibyte: Use hweight8 instead of counting bits

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/637/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>