MIPS: fix duplicated slashes for Platform file path

platform-y accumulates platform names with a slash appended.
The current $(patsubst ...) ends up with doubling slashes.

GNU Make still include Platform files, but in case of an error,
a clumsy file path is displayed:

  arch/mips/loongson2ef//Platform:36: *** only binutils >= 2.20.2 have needed option -mfix-loongson2f-nop.  Stop.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Author: masahir0y

arch/mips/Kbuild.platforms

@@ -37,4 +37,4 @@ platform-$(CONFIG_MACH_TX49XX)		+= txx9/
 platform-$(CONFIG_MACH_VR41XX)		+= vr41xx/
 
 # include the platform specific files
-include $(patsubst %, $(srctree)/arch/mips/%/Platform, $(platform-y))
+include $(patsubst %/, $(srctree)/arch/mips/%/Platform, $(platform-y))