media: staging: media: tegra-vde: Manually pack UAPI structures

The __packed macro isn't available in userspace with the kernel headers.
Checkpatch asks to use the macro, which is unwanted in a case of a UAPI
header. There is no much benefit in a tight packing of the structures,
hence let's pack them manually to cleanup things a tad. Note that there
is no old-stable userspace that will suffer from this change, hence it's
fine to change the ABI. In a result also more space is reserved for a
possible future expansion of the UAPI as it was already shown that more
fields will be needed for a later SoC generations.

Suggested-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>