drm/i915: don't conflate is_dgfx with fake lmem

When using fake lmem for tests, we are overriding the setting in
device info for dgfx devices. Current users of IS_DGFX() except one are
correct. However, as we add support for DG1, we are going to use it in
additional places to trigger dgfx-only code path.

In future if we need we can use HAS_LMEM() instead of IS_DGFX() in the
places that make sense to also contemplate fake lmem use.

v2: update gen8_gmch_probe() to use HAS_LMEM(): we need to steal the
mappable aperture later(which is fine since it doesn't exist on "DGFX"),
and use it as a substitute for LMEMBAR. The !mappable aperture property
is also useful since it exercises some other parts of the code too.
(Matthew Auld)

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201001063917.3133475-1-lucas.demarchi@intel.com

drivers/gpu/drm/i915/gt/intel_ggtt.c

@@ -835,7 +835,7 @@ static int gen8_gmch_probe(struct i915_ggtt *ggtt)
 	u16 snb_gmch_ctl;
 
 	/* TODO: We're not aware of mappable constraints on gen8 yet */
-	if (!IS_DGFX(i915)) {
+	if (!HAS_LMEM(i915)) {
 		ggtt->gmadr = pci_resource(pdev, 2);
 		ggtt->mappable_end = resource_size(&ggtt->gmadr);
 	}

drivers/gpu/drm/i915/i915_drv.c

@@ -840,9 +840,7 @@ int i915_driver_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 		    i915->params.fake_lmem_start) {
 			mkwrite_device_info(i915)->memory_regions =
 				REGION_SMEM | REGION_LMEM | REGION_STOLEN;
-			mkwrite_device_info(i915)->is_dgfx = true;
 			GEM_BUG_ON(!HAS_LMEM(i915));
-			GEM_BUG_ON(!IS_DGFX(i915));
 		}
 	}
 #endif