[media] msi3101: remove unused variable assignment

Coverity CID 1196508: Unused pointer value (UNUSED_VALUE)
Pointer "bandwidth" returned by "v4l2_ctrl_find(&s->hdl, 10619148U)"
is overwritten.

Reported-by:  <scan-admin@coverity.com>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>