leds: qpnp-wled: add external pfet sc support

WLED can be gated with an external pfet for
short circuit protection. Enable this based on
platform data.

Remove the support for dim shape which is not
supported by the hardware.

Change-Id: Ibd706b65c746c5e5eba31ea72dc387cf0beafe94
Signed-off-by: Mohan Pallaka <mpallaka@codeaurora.org>