drm/i915/dg1: Reserve first 1MB of local memory

drm/i915/dg1: Reserve first 1MB of local memory

On DG1 A0/B0 steppings the first 1MB of local memory must be reserved.
One reason for this is that the 0xA0000-0xB0000 range is not accessible
by the display, probably since this region is redirected to another
memory location for legacy VGA compatibility.

BSpec: 50586
Testcase: igt/kms_big_fb/linear-64bpp-rotate-0

v2:
- Reserve the memory on B0 as well.

v3: replace DRM_DEBUG/DRM_ERROR with drm_dbg/drm_err

v4: fix the insanity

Signed-off-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20210127131417.393872-5-matthew.auld@intel.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>