MIPS: Loongson: Add module info to the loongson2_clock driver

This patch fixes a kernel warning when loading the the loongson2_clock
driver:

"Feb 25 23:42:27 localhost kernel: [    4.965000] loongson2_clock: module
license 'unspecified' taints kernel."

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Reported-by: Liu Shiwei <liushiwei@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/1045/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>