clk: mediatek: fixup test-building of MediaTek clock drivers

Let the build system looking into the directiory where the clock drivers
resides for the COMPILE_TEST alternative dependency allows test-building
the drivers.
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

drivers/clk/Makefile

@@ -67,7 +67,7 @@ obj-$(CONFIG_ARCH_MXC)			+= imx/
 obj-$(CONFIG_MACH_INGENIC)		+= ingenic/
 obj-$(CONFIG_ARCH_KEYSTONE)		+= keystone/
 obj-$(CONFIG_MACH_LOONGSON32)		+= loongson1/
-obj-$(CONFIG_ARCH_MEDIATEK)		+= mediatek/
+obj-y					+= mediatek/
 obj-$(CONFIG_COMMON_CLK_AMLOGIC)	+= meson/
 obj-$(CONFIG_MACH_PIC32)		+= microchip/
 ifeq ($(CONFIG_COMMON_CLK), y)