Add Ingenic X1830 system type.

[Zhou Yanjie]

1.Add X1830 system type for cat /proc/cpuinfo to give out X1830.
2.Add "PRID_IMP_XBURST_REV2" (X1830 belongs PRID_IMP_XBURST_REV2)
  and rename "PRID_IMP_XBURST" to "PRID_IMP_XBURST_REV1".