[vector] Remove AArch64 SVE related code

[Yang Zhang]

Hi,

AArch64 SVE changes have been pushed jdk/master for review [1]. To
reduce conflicts with jdk master, remove AArch64 SVE related code.
Code merge issue in AArch64 backend is also fixed.

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

[1] http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2020-March/037628.html

Regards
Yang