This patch adds basic options for MIPS CPUFreq support.

Since the cp0 timer's frequency is based on the processor clockrate it can
not be used with CPUFReq; an additional external timer is required.
Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: cpufreq@vger.kernel.org,
Cc: Dave Jones <davej@redhat.com>,
Cc: Dominik Brodowski <linux@dominikbrodowski.net>,
Cc: yanh@lemote.com
Cc: huhb@lemote.com,
Patchwork: http://patchwork.linux-mips.org/patch/659/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>