media: v4l2-compat-ioctl32: initialize a reserved field

The get_v4l2_create32() function is missing a logic with
would be cleaning a reserved field, causing v4l2-compliance
to complain:

 Buffer ioctls (Input 0):
		fail: v4l2-test-buffers.cpp(506): check_0(crbufs.reserved, sizeof(crbufs.reserved))
	test VIDIOC_REQBUFS/CREATE_BUFS/QUERYBUF: FAIL

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>