Allow setting the same timings as the current timings (i.e., do nothing in that
case). The code was actually there, but the vb2_is_busy() call was done before
the timings check instead of afterwards.

Found by v4l2-compliance.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>