MIPS: GIC: Remove GIC_FLAG_IPI

irq-gic.c:gic_get_int() masks out interrupts from the pending set which
aren’t in the pcpu_mask. Only interrupts marked with GIC_FLAG_IPI were
set in pcpu_mask, meaning that peripheral interrupts also had to be
marked as IPIs. Remove the use of GIC_FLAG_IPI and allow the flags
member of struct gic_intr_map to be zero.

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/7374/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>