arm: mmp: move pxa168 clock definition to separated file

move pxa168 clock definition to another file. Then pxa168 can
choose common clock framework or private clock framework.

Signed-off-by: Chao Xie <xiechao.mail@gmail.com>
Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>
diff --git a/arch/arm/mach-mmp/Makefile b/arch/arm/mach-mmp/Makefile
index 815c3e7..bb63f86 100644
--- a/arch/arm/mach-mmp/Makefile
+++ b/arch/arm/mach-mmp/Makefile
@@ -11,6 +11,7 @@
 
 ifeq ($(CONFIG_COMMON_CLK), )
 obj-y				+= clock.o
+obj-$(CONFIG_CPU_PXA168)	+= clock-pxa168.o
 endif
 ifeq ($(CONFIG_PM),y)
 obj-$(CONFIG_CPU_PXA910)	+= pm-pxa910.o