gallium/aux/util/u_surface.c: Fix warning

_surface.c: In function 'util_copy_rect':
u_surface.c:101:37: warning: comparison between signed and unsigned
integer expressions [-Wsign-compare]
    if (width == dst_stride && width == src_stride)

Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Signed-off-by: Jakob Bornecrantz <jakob@collabora.com>

src/gallium/auxiliary/util/u_surface.c

@@ -98,7 +98,7 @@ util_copy_rect(ubyte * dst,
    src += src_y * src_stride_pos;
    width *= blocksize;
 
-   if (width == dst_stride && width == src_stride)
+   if (width == dst_stride && (int)width == src_stride)
       memcpy(dst, src, height * width);
    else {
       for (i = 0; i < height; i++) {