drm/i915: Remove some legacy mmio accessors from interrupt handling

Mostly in gen11 interrupt handling and a couple neighbouring functions
which were easy since uncore local was already available.

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/20190704121756.27824-2-tvrtko.ursulin@linux.intel.com