ARM: mediatek: clean up mach-mediatek/Makefile

Kbuild descends into arch/arm/mach-mediatek/Makefile only when
CONFIG_ARCH_MEDIATEK is enabled.  So, obj-$(CONFIG_ARCH_MEDIATEK)
is always equivalent to obj-y in this Makefile.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>

arch/arm/mach-mediatek/Makefile

-ifeq ($(CONFIG_SMP),y)
-obj-$(CONFIG_ARCH_MEDIATEK) += platsmp.o
-endif
-obj-$(CONFIG_ARCH_MEDIATEK) += mediatek.o
+obj-$(CONFIG_SMP)	+= platsmp.o
+obj-y			+= mediatek.o