MIPS: Bonito64: Make Loongson independent from Bonito64 code.

The built-in Loongson 2E/2F northbridge in is bonito64-compatible but not
identical with it.  To avoid influencing the original bonito64 support and
make the loongson support more maintainable, it's better to separate the
Bonito64 code from the Loongson code.

This also prepares the kernel for the coming Loongson 2f machines family
support.

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: Linux-MIPS <linux-mips@linux-mips.org>
Cc: yanh@lemote.com
Cc: huhb@lemote.com
Cc: Zhang Le <r0bertz@gentoo.org>
Cc: zhangfx@lemote.com,
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>