drm/radeon/kms: add support to atom parser for FB read/write

FB read/write really doesn't need to access the actual VRAM, we
can just use a scratch area. This is required for using atom displayport
calls later.

Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
index a014ba4..60ee6a8 100644
--- a/drivers/gpu/drm/radeon/radeon_device.c
+++ b/drivers/gpu/drm/radeon/radeon_device.c
@@ -481,11 +481,13 @@
 
 	rdev->mode_info.atom_context = atom_parse(atom_card_info, rdev->bios);
 	radeon_atom_initialize_bios_scratch_regs(rdev->ddev);
+	atom_allocate_fb_scratch(rdev->mode_info.atom_context);
 	return 0;
 }
 
 void radeon_atombios_fini(struct radeon_device *rdev)
 {
+	kfree(rdev->mode_info.atom_context->scratch);
 	kfree(rdev->mode_info.atom_context);
 	kfree(rdev->mode_info.atom_card_info);
 }