MIPS: ralink: Don't include objects twice

With the change of platform file inclusion object were included via
platform-y and core-y. Remove the core-y part to fix it.

Fixes: 26bff9eb ("MIPS: Only include the platformfile needed")
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/ralink/Platform

 #
 # Ralink SoC common stuff
 #
-core-$(CONFIG_RALINK)		+= arch/mips/ralink/
 cflags-$(CONFIG_RALINK)		+= -I$(srctree)/arch/mips/include/asm/mach-ralink
 
 #