MIPS: Loongson 2F: Cleanup the #if clauses

This patch adds two new kernel options: CPU_SUPPORTS_CPUFREQ and
CPU_SUPPORTS_ADDRWINCFG to describe the new features of Loongons 2F and
replaces the several ugly #if clauses by them.

These two options will be utilized by the future loongson revisions and
related drivers such as the coming Loongson 2F CPUFreq driver.

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: Wu Zhangjin <wuzhangjin@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>