video: fbdev: omap: Make it CCF clk API compatible

OMAP1 LCDC drivers now omit clk_prepare/unprepare() steps, not supported
by OMAP1 custom implementation of clock API.  However, non-CCF stubs of
those functions exist for use on such platforms until converted to CCF.

Update the drivers to be compatible with CCF implementation of clock API.

Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Signed-off-by: Helge Deller <deller@gmx.de>