V4L/DVB (11574): uvcvideo: fill reserved fields with zero of VIDIOC_QUERYMENU

When querying menu items with VIDIOC_QUERYMENU the reserved field
is not set to zero as required by V4L2 API revision 0.24 [1].
Add this fill.

The patch was tested with v4l-test 0.11 [2] with CNF7129 webcam found
on EeePC 901.

References:
[1] V4L2 API specification, revision 0.24
    http://v4l2spec.bytesex.org/spec/r13317.htm#V4L2-QUERYMENU

[2] v4l-test: Test environment for Video For Linux Two API
    http://v4l-test.sourceforge.net/

[Modified by Laurent Pinchart]

Use u32 instead of __u32 in non-exported kernel code.

Signed-off-by: Márton Németh <nm127@freemail.hu>
Signed-off-by: Laurent Pinchart <laurent.pinchart@skynet.be>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>