boston: Setup memory ranges in FDT provided to Linux

The boston memory map isn't suited to the simple "all memory starting
from 0" approach that the MIPS arch_fixup_fdt() implementation takes.
Instead we need to indicate the first 256MiB of DDR from 0 and the rest
from 0x90000000. Implement ft_board_setup to do that.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/mips/Kconfig

@@ -97,6 +97,7 @@ config TARGET_BOSTON
 	select MIPS_CM
 	select MIPS_L1_CACHE_SHIFT_6
 	select MIPS_L2_CACHE
+	select OF_BOARD_SETUP
 	select SUPPORTS_BIG_ENDIAN
 	select SUPPORTS_LITTLE_ENDIAN
 	select SUPPORTS_CPU_MIPS32_R1