[vector] Update AbsV match rule for AArch64 NEON

[Yang Zhang (Arm Technology China)]

Hi

Could anyone please help to review this patch?

Webrev: http://cr.openjdk.java.net/~yzhang/vectorapi/vectorapi.absv/webrev.00/

In this patch, AbsV nodes are seperated to AbsVB/AbsVS/AbsVI/AbsVL. Instruction
encodings are also updated..

Regards,
Yang