qcom: spmi-wled: Move OVP and SC irqs out of config

Currently, Over-voltage protection (OVP) fault and Short-circuit
(SC) interrupts are defined under WLED configuration. Move them
out of it and keep them under the main data structure.

While at it, remove an unused variable in handle_ovp_fault().

Change-Id: I3c48141a1d1fd882d5d281e6728bd647519b4029
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>