[vector-unstable] Fix build failure in vector-unstable branch on AArch64

[Yang Zhang]

Hi,

Could you please help to review this change?

The failure is:
src/hotspot/cpu/aarch64/sharedRuntime_aarch64.cpp:827: undefined
reference to `Matcher::supports_vector_calling_convention()'

vector_calling_convention related code is used for SVML stubs and
their support. In [1], this code has been removed in vector-unstable.
Review thread is in [2]. But in vectorIntrinsics branch, this code is
reserved. When sync-up vector-unstable and vectorIntrinsics, there
might be some issues.

To fix this failure, all vector_calling_convention related code is
removed.

Webrev: http://cr.openjdk.java.net/~yzhang/vectorapi/vectorapi.bugfix3/webrev.00/

[1] https://hg.openjdk.java.net/panama/dev/rev/1e0fef073cfb
[2] https://mail.openjdk.java.net/pipermail/panama-dev/2020-March/007969.html

Regards
Yang