MIPS: X1830: Add X1830 system type.

MIPS: X1830: Add X1830 system type.

1.Add X1830 system type for cat /proc/cpuinfo to give out X1830.
2.Change "PRID_IMP_XBURST" to "PRID_IMP_XBURST_REV1" and add a
  new "PRID_IMP_XBURST_REV2" for new Ingenic CPUs which has
  XBurst with MXU2 SIMD ISA.

Notice:
1."PRID_IMP_XBURST_REV2" is corresponds to the latest XBurst
  processor with 128bit MXU2 SIMD instruction set, not the upcoming
  XBurst2 processor. This version of the processors fixes issues
  such as BTB and HPTLB.
2.In order to simplify and reuse the code, the "c->cputype" and
  the "c->writecombine" and the "__cpu_name[cpu]" in the original
  "PRID_IMP_XBURST" (now is "PRID_IMP_XBURST_REV1") are removed,
  and the corresponding settings are abtained through fall-through
  to "PRID_IMP_XBURST_REV2", which will cause the name that was
  previously mistakenly called "JZRISC" to become to the real name
  "XBurst".

Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>
Signed-off-by: Paul Burton <paulburton@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: yamada.masahiro@socionext.com
Cc: tglx@linutronix.de
Cc: chenhc@lemote.com
Cc: tbogendoerfer@suse.de
Cc: paul.burton@mips.com
Cc: paul@crapouillou.net
Cc: jhogan@kernel.org
Cc: fancer.lancer@gmail.com
Cc: ralf@linux-mips.org
Cc: jiaxun.yang@flygoat.com