drm/i915: make mappable struct resource centric

Now that we are using struct resource to track the stolen region, it is
more convenient if we track the mappable region in a resource as well.

v2: prefer iomap and gmadr naming scheme
    prefer DEFINE_RES_MEM

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171211151822.20953-8-matthew.auld@intel.com
diff --git a/drivers/gpu/drm/i915/intel_overlay.c b/drivers/gpu/drm/i915/intel_overlay.c
index 1b397b4..41e9465 100644
--- a/drivers/gpu/drm/i915/intel_overlay.c
+++ b/drivers/gpu/drm/i915/intel_overlay.c
@@ -219,7 +219,7 @@ intel_overlay_map_regs(struct intel_overlay *overlay)
 	if (OVERLAY_NEEDS_PHYSICAL(dev_priv))
 		regs = (struct overlay_registers __iomem *)overlay->reg_bo->phys_handle->vaddr;
 	else
-		regs = io_mapping_map_wc(&dev_priv->ggtt.mappable,
+		regs = io_mapping_map_wc(&dev_priv->ggtt.iomap,
 					 overlay->flip_addr,
 					 PAGE_SIZE);
 
@@ -1508,7 +1508,7 @@ intel_overlay_map_regs_atomic(struct intel_overlay *overlay)
 		regs = (struct overlay_registers __iomem *)
 			overlay->reg_bo->phys_handle->vaddr;
 	else
-		regs = io_mapping_map_atomic_wc(&dev_priv->ggtt.mappable,
+		regs = io_mapping_map_atomic_wc(&dev_priv->ggtt.iomap,
 						overlay->flip_addr);
 
 	return regs;