ARM: OMAP3: vc: fix 'or' always true warning

Fix the warning:
arch/arm/mach-omap2/vc.c:302:47: warning: logical ‘or’ of collectively exhaustive tests is always true [-Wlogical-op]

As we're toggling both CLKREQ and OFFMODE, we should also be checking
OFFMODE.

Signed-off-by: Frans Klaver <fransklaver@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>