[MIPS] Fix sparse warnings about too big constants.

Fix following warnings:
linux/arch/mips/kernel/setup.c:249:12: warning: constant 0xffffffff00000000 is so big it is unsigned long
linux/arch/mips/kernel/cpu-bugs64.c:209:10: warning: constant 0xffffffffffffdb9a is so big it is unsigned long
linux/arch/mips/kernel/cpu-bugs64.c:227:10: warning: constant 0xffffffffffffdb9a is so big it is unsigned long
linux/arch/mips/kernel/cpu-bugs64.c:283:10: warning: constant 0xffffffffffffdb9a is so big it is unsigned long
linux/arch/mips/kernel/cpu-bugs64.c:299:10: warning: constant 0xffffffffffffdb9a is so big it is unsigned long

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