RFR: 8287394: AArch64: Remove cbuf parameter from far_call/far_jump/trampoline_call

[Evgeny Astigeevich]

`far_call`/`far_jump`/`trampoline_call` have parameter `cbuf` with the default value `NULL`. We always call `far_call`/`far_jump` with `NULL`. We call  `trampoline_call` with either `NULL` or the `CodeBuffer` currently used by `MacroAssembler`. If not `NULL` we mark a trampoline call position.

Andrew Haley(@theRealAph) in https://github.com/openjdk/jdk/pull/8564#discussion_r871062342 suggests to remove it.

This PR removes the parameter. In the case of `trampoline_call` we explicitly return the position of the generated trampoline calls. All places using the position of the generated trampoline call are updated.

Tested with release and fastdebug builds:
- `gtest`: Passed.
- `tier1`/`tier2`: Passed.

-------------

Commit messages:
 - 8287394: AArch64: Remove the cbuf argument from far_call/far_jump/trampoline_call

Changes: https://git.openjdk.org/jdk/pull/10244/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10244&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8287394
  Stats: 27 lines in 5 files changed: 0 ins; 9 del; 18 mod
  Patch: https://git.openjdk.org/jdk/pull/10244.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10244/head:pull/10244

PR: https://git.openjdk.org/jdk/pull/10244