Build fix for missing symbol.

Cc: qemu-stable@nongnu.org
Fixes: dad2f2f5 ("tcg/sparc64: Disable TCG_TARGET_HAS_extr_i64_i32")
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>