MIPS: Ingenic XBurst Jz4740 processor support

Jz4740 is a multimedia application processor targeting for mobile
devices like e-Dictionary, eBook, portable media player (PMP) and
GPS navigator.  Jz4740 is powered by Ingenic 360 MHz XBurst CPU core
(JzRISC), in which RISC/SIMD/DSP hybrid instruction set architecture
provides high integration, high performance and low power consumption.

JzRISC incorporated in Jz4740 is the advanced and power-efficient
32-bit RISC core, compatible with MIPS32, with 16K I-Cache and 16K
D-Cache, and can operate at speeds up to 400 MHz.

On-chip modules such as LCD controller, embedded audio codec, multi-
channel SAR-ADC, AC97/I2S controller and camera I/F offer a rich
suite of peripherals for multimedia application.  NAND controller
(SLC/MLC), USB (host 1.1 and device 2.0), UART, I2C, SPI, etc. are
also available.

For more info about Ingenic XBurst Jz4740:
  http://en.ingenic.cn/eng/
  http://www.linux-mips.org/wiki/Ingenic



This patch introduces XBurst CPU support in U-Boot.  It's compatible
with MIPS32, but requires a bit different cache maintenance, timer
routines, and boot mechanism using USB boot tool, so XBurst support
can go into a separate new home, cpu/xburst/.

Signed-off-by: Xiangfu Liu <xiangfu@openmobilefree.net>
Acked-by: Daniel <zpxu@ingenic.cn>
Signed-off-by: Shinya Kuribayashi <skuribay@pobox.com>