ARM: OMAP2/3: Change omapfb to use clkdev for dispc and rfbi, v2

This makes the framebuffer work on omap3.

Also fix the clk_get usage for checkpatch.pl
"ERROR: do not use assignment in if condition".

Cc: Imre Deak <imre.deak@nokia.com>
Cc: linux-fbdev-devel@lists.sourceforge.net
Acked-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Tony Lindgren <tony@atomide.com>