MIPS: c-r4k: Avoid small flush_icache_range SMP calls

Avoid SMP calls for flushing small icache ranges. On non-CM platforms,
and CM platforms too after we make r4k_on_each_cpu() take the cache op
type into account, it will be called on multiple CPUs due to the
possibility that local_r4k_flush_icache_range_ipi() could do
non-globalized indexed cache ops. This rougly copies the range size
check out into r4k_flush_icache_range(), which can disallow indexed
cache ops and allow r4k_on_each_cpu() to skip the SMP call.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Leonid Yegoshin <leonid.yegoshin@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/13805/


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