[media] rc: Introduce hix5hd2 IR transmitter driver

IR transmitter driver for Hisilicon hix5hd2 soc

By default all protocols are disabled.
For example nec decoder can be enabled by either
1. ir-keytable -p nec
2. echo nec > /sys/class/rc/rc0/protocols
See see Documentation/ABI/testing/sysfs-class-rc

[mchehab@osg.samsung.com: Add a fixup for the driver to compile on
 archs that don't provide writel_relaxed() macro]
Signed-off-by: Guoxiong Yan <yanguoxiong@huawei.com>
Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>