[MIPS] Separate performance counter interrupts

Support for performance counter overflow interrupt that is on a separate
interrupt from the timer.

Signed-off-by: Chris Dearman <chris@mips.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --cc arch/mips/kernel/smp-mt.c
Simple merge

diff --cc arch/mips/kernel/time.c
Simple merge

diff --cc arch/mips/mips-boards/generic/time.c
Simple merge

diff --cc arch/mips/oprofile/op_model_mipsxx.c
Simple merge