[media] ir-hix5hd2: fix build on c6x arch

While not all archs have readl_relaxed, we need to add a hack at the
driver to allow it to COMPILE_TEST on all archs:

	drivers/media/rc/ir-hix5hd2.c: In function ‘hix5hd2_ir_config’:
	drivers/media/rc/ir-hix5hd2.c:100:2: error: implicit declaration of function ‘readl_relaxed’ [-Werror=implicit-function-declaration]

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>