drm/i915/icl: Icelake interrupt register addresses and bits

MMIO addresses and register definition for the new interrupt
registers in Gen11.

v2: Removed spelt out VCS and VECS bit definitions. (Daniel Vetter)
v3: Adjust VCS and VECS. (Daniele Ceraolo Spurio)
v4: Bikeshedding (Paulo).

Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180109232336.11029-5-paulo.r.zanoni@intel.com