ocfb: fix tgdel and tvdel timing parameters

According to the ocfb documentation:
Fix tgdel HW param should be left margin, not right.
Fix tvdel HW param should upper margin, not lower.

This seems to fix lock issues on certain monitors (tested on a
slightly customized IP, but the FPGA guy said that it should
be the same wrt this changes).

Signed-off-by: Andrea Merello <andrea.merello@gmail.com>
Acked-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>