[media] OMAP_VOUT: Fix check in reqbuf for buf_size allocation

The commit 383e4f69 makes reqbuf prevent
requesting a larger size buffer than what is allocated at kernel boot during
omap_vout_probe.

In omap_vout_buffer_setup callback API, the requested size is compared with
vout->buffer_size, this isn't correct as vout->buffer_size is later set to the
size requested in reqbuf. When the video device is opened the next time, this
check will prevent us to allocate a buffer which is larger than what we requested
the last time.

Don't use vout->buffer_size, always check with the parameters video1_bufsize
or video2_bufsize.

Signed-off-by: Archit Taneja <archit@ti.com>
Acked-by: Vaibhav Hiremath <hvaibhav@ti.com>
Signed-off-by: Vaibhav Hiremath <hvaibhav@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>