[MIPS] Change names of local variables to silence sparse

This patch is an workaround for these sparse warnings:

linux/include/linux/calc64.h:25:17: warning: symbol '__quot' shadows an earlier one
linux/include/linux/calc64.h:25:17: originally declared here
linux/include/linux/calc64.h:25:17: warning: symbol '__mod' shadows an earlier one
linux/include/linux/calc64.h:25:17: originally declared here

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>