drm/vmwgfx: Fix a 64bit regression on svga3

Register accesses are always 4bytes, accidently this was changed to
a void pointer whwqich badly breaks 64bit archs when running on top
of svga3.

Fixes: 2cd80dbd3551 ("drm/vmwgfx: Add basic support for SVGA3")
Signed-off-by: Zack Rusin <[e-mail]>
Reviewed-by: Martin Krastev <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
(cherry picked from commit 87360168759879d68550b0c052bbcc2a0339ff74)
Signed-off-by: Thomas Zimmermann <[e-mail]>

drivers/gpu/drm/vmwgfx/vmwgfx_drv.h

···
 	resource_size_t vram_start;
 	resource_size_t vram_size;
 	resource_size_t prim_bb_mem;
-	void __iomem *rmmio;
+	u32 __iomem *rmmio;
 	u32 *fifo_mem;
 	resource_size_t fifo_mem_size;
 	uint32_t fb_max_width;