V4L2: ov7670: fix a wrong index, potentially Oopsing the kernel from user-space

V4L2: ov7670: fix a wrong index, potentially Oopsing the kernel from user-space

commit cfece5857ca51d1dcdb157017aba226f594e9dcf upstream.

Commit 75e2bdad8901a0b599e01a96229be922eef1e488 "ov7670: allow
configuration of image size, clock speed, and I/O method" uses a wrong
index to iterate an array. Apart from being wrong, it also uses an
unchecked value from user-space, which can cause access to unmapped
memory in the kernel, triggered by a normal desktop user with rights to
use V4L2 devices.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
[bwh: Backported to 3.2:
 - Adjust filename
 - win_sizes array is static, not per-device]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>