RFR: 8343430: RISC-V: C2: Remove old trampoline call [v6]

[Fei Yang]

> Hi, please consider this cleanup change.
> 
> The old trampoline call on linux-riscv64 is disabled by default after: https://bugs.openjdk.org/browse/JDK-8332689.
> And the new solution (load target address from stub and call) has been baked in jdk master for quite some time.
> This propose to remove the old trampoline call related logic so that the code will be cleaner and easier to maintain.
> As we are still using `trampoline_stub_Relocation` for the stub, I kept using the original `emit_trampoline_stub` name.
> 
> Testing on linux-riscv64:
> - [x] tier1-tier3 (release)
> - [x] hotspot:tier1 (fastdebug)

Fei Yang has updated the pull request incrementally with one additional commit since the last revision:

  More naming

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/21822/files
  - new: https://git.openjdk.org/jdk/pull/21822/files/36664c11..5e5655bd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21822&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21822&range=04-05

  Stats: 4 lines in 3 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/21822.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21822/head:pull/21822

PR: https://git.openjdk.org/jdk/pull/21822