[MIPS] Yosemite: Fix warning.

arch/mips/pmc-sierra/yosemite/smp.c: In function 'titan_mailbox_irq':
arch/mips/pmc-sierra/yosemite/smp.c:112: warning: 'status' may be used uninitialized in this function

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