MIPS: GIC: Generalise check for pending interrupts

MIPS: GIC: Generalise check for pending interrupts

Move most of the functionality of gic_get_int() into a new function
gic_get_int_mask() which takes a bitmask of interrupts in which the
caller is interested, and returns the subset which are pending for the
current CPU.

This allows CP0 IRQ dispatch routines to check only the GIC interrupts
which are routed to a particular CPU interrupt input.

gic_get_int() is reimplemented using gic_get_int_mask() and is retained
for use by any platforms for which gic_get_int() is sufficient.

Signed-off-by: Jeffrey Deans <jeffrey.deans@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7376/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>