IRQENABLE_SET registers are (usually) not meant to be read, only written
to. The current driver needlessly uses read-modify-write cycle to enable
IRQ bits.

The read-modify-write has no bad side effects here, but it's still
better to clean this up by only using write.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Benoit Parrot <bparrot@ti.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>