power: smb5: Modify WDOG SNARL IRQ enable/disable flow

WDOG SNARL IRQ is required for SW Thermal Regulation WA only. Hence,
remove run time enable/disable logic of WDOG_SNARL_IRQ and add support
to disable WDOG_SNARL_IRQ post its registration in case SW Thermal
Regulation WA is not required.

Change-Id: I3012450e6c7e57298e325ec7e2d89ddddf85c2ce
Signed-off-by: Umang Agrawal <uagrawal@codeaurora.org>