gallium/aux/util/u_format.c: Fix one -Wunused-param warning

This warning was issued only in release mode. Fix it by fake-using the
parameter.

Signed-off-by: Gert Wollny <gw.fossdev@gmail.com>
Reviewed-by: Brian Paul <brianp@vmware.com> (v1)

src/gallium/auxiliary/util/u_format.c

@@ -249,6 +249,8 @@ util_format_is_supported(enum pipe_format format, unsigned bind)
        util_format_is_float(format)) {
       return FALSE;
    }
+#else
+   (void)bind;
 #endif
 
    return TRUE;