Input: clean up Makefile (use input-core-y)

The proper way to specify multi-source object is to use <name>-y instead
of <name>-obj (which is deprecated) as it allows conditional inclusion
of modules in the list.
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/Makefile

@@ -5,7 +5,7 @@
 # Each configuration option enables a list of files.
 
 obj-$(CONFIG_INPUT)		+= input-core.o
-input-core-objs := input.o input-compat.o ff-core.o
+input-core-y := input.o input-compat.o ff-core.o
 
 obj-$(CONFIG_INPUT_FF_MEMLESS)	+= ff-memless.o
 obj-$(CONFIG_INPUT_POLLDEV)	+= input-polldev.o