OMAPDSS: cleanup WB enable/is_enabled functions
OMAPDSS: cleanup WB enable/is_enabled functions

Instead of doing direct register reads/writes, dispc_wb_enable() and
dispc_wb_is_enabled() functions can use the common overlay functions to
set and check the enable bit.

Signed-off-by: Tomi Valkeinen <e1ca4dbb8be1acaf20734fecd2da10ed1d46a9bb@ti.com>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas