[media] coda: add missing header dependencies

We get 1 warning when building kernel with W=1:
drivers/media/platform/coda/coda-h264.c:22:5: warning: no previous prototype for 'coda_h264_padding' [-Wmissing-prototypes]

In fact, this function is declared in coda.h, so this patch
add missing header dependencies.

Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>