qcom: spmi-wled: Add support for OVP interrupt handling

WLED peripheral has over voltage protection(OVP) circuitry and the OVP
fault is notified through an interrupt. Though this fault condition rising
due to an incorrect hardware configuration is mitigated in the hardware,
it still needs to be detected and handled. Add support for it.

When WLED module is enabled, keep OVP fault interrupt disabled for 10 ms to
account for soft start delay.

Change-Id: I2f331b94f7e7e740cebb2ebc420f90c5a3946df7
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>