leds: qpnp-wled: add support for enabling AMOLED panels

As per the hardware documentation, certain registers in
the control block need to be over-written for supporting
AMOLED panels. Add support of configuring these registers.

Change-Id: I2a68b4033e2680290479523acd51a4472ad21e3a
Signed-off-by: Himanshu Aggarwal <haggarwa@codeaurora.org>