MIPS: Make a needlessly global symbol static in arch/mips/kernel/smp.c
The variable cpu_callin_map is needlessly defined global, so let's
make it static now.
Build-tested using malta_defconfig.
Signed-off-by: Dmitri Vorobiev <dmitri.vorobiev@movial.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>