[media] staging: omap4iss: copy paste error in iss_get_clocks

It makes more sense to return PTR_ERR(iss->iss_ctrlclk) here. The
current code looks like an oversight in pasting the block just above
this one.

Signed-off-by: Vitaly Osipov <vitaly.osipov@gmail.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>