media: staging: tegra-vde: Correct included header

This is Open Firmware driver, hence 'of_device.h' should be included
instead of 'platform_device.h'. Right now OF headers happen to be included
indirectly and this may break in the future, so let's correct the header.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>