drm: switch drm_fb_memcpy_dstclip to accept __iomem dst

Not all archs have the __io_virt() macro, so cirrus can't simply convert
pointers that way.  The drm format helpers have to use memcpy_toio()
instead.

This patch makes drm_fb_memcpy_dstclip() accept a __iomem dst pointer
and use memcpy_toio() instead of memcpy().  With that separating out the
memcpy loop into the drm_fb_memcpy_lines() helper isn't useful any more,
so move the code back into the calling functins.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20190410063815.17062-2-kraxel@redhat.com

drivers/gpu/drm/cirrus/cirrus.c

@@ -307,7 +307,7 @@ static int cirrus_fb_blit_rect(struct drm_framebuffer *fb,
 		return -ENOMEM;
 
 	if (cirrus->cpp == fb->format->cpp[0])
-		drm_fb_memcpy_dstclip(__io_virt(cirrus->vram),
+		drm_fb_memcpy_dstclip(cirrus->vram,
 				      vmap, fb, rect);
 
 	else if (fb->format->cpp[0] == 4 && cirrus->cpp == 2)