media: sunxi-cir: Factor out hardware initialization

In preparation for adding suspend/resume hooks, factor out the hardware
initialization from the driver probe/remove functions.

The timeout programmed during init is taken from the `struct rc_dev` so
it is maintained across an exit/init cycle.

This resolves some trivial issues with the probe function: throwing away
the error from clk_prepare_enable and using the wrong type for the
temporary register value.

It also fixes the order of the remove function to unregister the RC
device before turning off the hardware. This prevents userspace from
triggering register writes (via LIRC_SET_REC_TIMEOUT) while the hardware
is disabled.

Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>