MIPS: Do not initialise globals to 0

Fix the following checkpatch error:

ERROR: do not initialise globals to 0
#834: FILE: arch/mips/kernel/setup.c:834:
+int hw_coherentio = 0;	/* Actual hardware supported DMA coherency setting. */

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>