MIPS: Kconfig: refactor machine setup

Refactor machine setup like it is done on ARM. While on it,
also support "include <mach/file.h" for machine specific
header files.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>

arch/mips/Makefile

@@ -7,4 +7,9 @@ head-y := arch/mips/cpu/start.o
 libs-y += arch/mips/cpu/
 libs-y += arch/mips/lib/
 
-libs-$(CONFIG_SOC_AU1X00) += arch/mips/mach-au1x00/
+machine-$(CONFIG_SOC_AU1X00) += au1x00
+
+machdirs := $(patsubst %,arch/mips/mach-%/,$(machine-y))
+libs-y += $(machdirs)
+
+PLATFORM_CPPFLAGS += $(patsubst %,-I$(srctree)/%include,$(machdirs))