OMAP2+: voltage: enable VC bypass scale method when VC is initialized

VC is initialized first, set default scaling method to VC bypass.
If/when VP is initialized, default scaling method will be changed to
VP force-update.

Enabling VC bypass as default as soon as VC is initialized allows for
VC bypass scaling to work when no VP is configured/initialized for a
given voltage domain.

Signed-off-by: Kevin Hilman <khilman@ti.com>