[media] omap3isp: queue: Fix the dma_map_sg() return value check

dma_map_sg() can merge sglist entries, and can thus return a number of
mapped entries different than the original value. Don't consider this as
an error.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>