MIPS: smp-mt: Use common GIC IPI implementation

Rather than duplicating the GIC IPI send function, share the one already
used by CONFIG_MIPS_CPS & CONFIG_MIPS_CMP.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Paul Burton <paul.burton@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/6653/


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