0-Day tests found compilation error on x86.
Driver won't compile on x86_64 as "of_match_ptr" is
not found. Add missing include <linux/of.h>

At some point this fix was lost. So re-apply it.
Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Signed-off-by: Mark Brown <broonie@kernel.org>