OMAPDSS: DISPC: Remove dispc_mgr_set_pol_freq()

dispc_mgr_set_pol_freq() configures the fields in the register DISPC_POL_FREQo.
All these fields have been moved to omap_video_timings struct, and are now
programmed in dispc_mgr_set_lcd_timings(). These will be configured when timings
are applied via dss_mgr_set_timings().

Remove dispc_mgr_set_pol_freq() and it's calls from the interface drivers.

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