drm/vmwgfx: Handle vmalloc() failure in vmw_local_fifo_reserve()

commit f0c62e98 upstream.

If vmalloc() fails then we need to a bit of cleanup before returning.

Fixes: fb1d9738 ("drm/vmwgfx: Add DRM driver for VMware Virtual GPU")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>