OMAPDSS: RFBI: Maitain copy of rfbi timings in driver data

The RFBI driver currently relies on the omap_dss_device struct to receive the
rfbi specific timings requested by the panel driver. This makes the RFBI
interface driver dependent on the omap_dss_device struct.

Make the RFBI driver data maintain it's own rfbi specific timings field. The
panel driver is expected to call omapdss_rfbi_set_interface_timings() to
configure the rfbi timings before the interface is enabled.

Signed-off-by: Archit Taneja <archit@ti.com>