drm/i915: Rename ggtt_view as gtt_view

So far, different views (normal, partial, rotated and remapped)
into the same object are only supported for GGTT mappings.
But with the upcoming VM_BIND feature, PPGTT will also use the
partial view mapping. Hence rename ggtt_view to more generic
gtt_view.

Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
Acked-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220901183854.3446-1-niranjana.vishwanathapura@intel.com