drm/i2c: adv7511: Init regulators

ADV7533 requires a constant supply to the AVDD and V3P3 pins for it
to function. The driver wrongly assumed that these will be enabled
all the time.

Configure these regulators during probe itself. We can later enable
and disable it dynamically.

Signed-off-by: Archit Taneja <architt@codeaurora.org>