drm/vmwgfx/vmwgfx_drv: Fix an error path in vmw_setup_pci_resources()

The devm_memremap() function never returns NULL, it returns error
pointers so the test needs to be fixed.  Also we need to call
pci_release_regions() to avoid a memory leak.

Fixes: be4f77ac

 ("drm/vmwgfx: Cleanup fifo mmio handling")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Zack Rusin <zackr@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/YA6FMboLhnE3uSvb@mwanda