MIPS: X2000: Add X2000 system type.

1.Add "PRID_COMP_INGENIC_13" and "PRID_IMP_XBURST2" for X2000.
2.Add X2000 system type for cat /proc/cpuinfo to give out X2000.

Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>