ARM: OMAP: board-4430sdp: Provide regulator to pwm-backlight

The pwm-backlight driver now takes a mandatory regulator that is gotten
during driver probe.  Initialize a dummy regulator to satisfy this
requirement.

Signed-off-by: Andrew Chew <achew@nvidia.com>
Tested-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
[tony@atomide.com: updated fixed regulator id to avoid errors]
Signed-off-by: Tony Lindgren <tony@atomide.com>