While running v4l2-compliance tests on vivid I suddenly got errors due to
a call to vmalloc_user with size 0 from vb2.

Digging deeper into the cause I discovered that this was due to the fact that
struct v4l2_plane_pix_format defines bytesperline as a __u16 instead of a __u32.

The test I was running selected a format of 4 * 4096 by 4 * 2048 with a 32
bit pixelformat.

So bytesperline was 4 * 4 * 4096 = 65536, which becomes 0 in a __u16. And
bytesperline * height is suddenly 0 as well. While the vivid driver may be
a virtual driver, it is to be expected that this limit will be hit for real
hardware as well in the near future: 8k deep-color video will already reach
it.

The solution is to change the type to __u32. The only drivers besides vivid
that use the multiplanar API are little-endian ARM and SH platforms (exynos,
ti-vpe, vsp1), so this is safe.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>