[PORT FROM R2] driver: intel_scu_watchdog: remove all gating from interrupt handler

[PORT FROM R2] driver: intel_scu_watchdog: remove all gating from interrupt handler

BZ: 21273

There was some lagacy gating code in the driver from the days
when the driver would do the initial setting of the clock.

Change-Id: Id5520a832cc7d0e90fe39876ede62bcbe5d6486c
Reviewed-on: http://android.intel.com:8080/33944
Reviewed-by: Chotard, Celine <celine.chotard@intel.com>
Tested-by: Chotard, Celine <celine.chotard@intel.com>
Reviewed-by: Lebouc, Christophe <christophe.lebouc@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>