drm/i915: Rework some interrupt handling functions to take intel_gt

Some interrupt handling functions already have gt in their names
suggesting them as obvious candidates to make them take struct intel_gt
instead of i915.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Co-developed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190704121756.27824-1-tvrtko.ursulin@linux.intel.com