Add a new kernel option for Lemote Loongson 2F family machines.

Lemote loongson2f family machines utilize the 2f revision of loongson
processor and the AMD CS5536 south bridge.

Family members include Fuloong 2F mini PC, Yeeloong 2F notebook, LingLoong
all-in-one PC and others.
Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: zhangfx@lemote.com
Cc: yanh@lemote.com
Cc: huhb@lemote.com
Cc: Nicholas Mc Guire <hofrat@hofr.at>
Cc: Arnaud Patard <apatard@mandriva.com>
Cc: loongson-dev@googlegroups.com
Cc: linux-mips@linux-mips.org
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>