MIPS: Add support for uncached accelerated mappings.

Loongson2f support video acceleration.

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/624/
Patchwork: http://patchwork.linux-mips.org/patch/625/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>