configure: remove loongson check inline asm and mips dependent

1.Loongson now have two series CPU supported MMI(Multi-Media Instruct).
  Loongson-3 designed multi-core have good performance in decoding.
  Loongson-2's support is comming soon.
2.Replaced loongson with loongson2 and loongson3.

Signed-off-by: ZhouXiaoyong <zhouxiaoyong@loongson.cn>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
