clk: pxa clocks build system fix

Fix the building of pxa clock drivers so that the files are actually
compiled if and only if COMMON_CLK was selected by the architecture.

This prevents conflicts with mach-pxa clock legacy implementation.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 8f3c04a..5eaf1b5 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -51,7 +51,7 @@
 endif
 obj-$(CONFIG_PLAT_ORION)		+= mvebu/
 obj-$(CONFIG_ARCH_MXS)			+= mxs/
-obj-$(CONFIG_ARCH_PXA)			+= pxa/
+obj-$(CONFIG_COMMON_CLK_PXA)		+= pxa/
 obj-$(CONFIG_COMMON_CLK_QCOM)		+= qcom/
 obj-$(CONFIG_ARCH_ROCKCHIP)		+= rockchip/
 obj-$(CONFIG_COMMON_CLK_SAMSUNG)	+= samsung/