RFR: 8293781: RISC-V: Clarify types of calls [v5]

[Yanhong Zhu]

> RISCV64 OpenJDK uses different types of calls in generated calls. It should be clarified what they are. And the PR also cleans up some out-of-date comments.
> 
> HotSpot tier1 tests passed.

Yanhong Zhu has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:

 - Merge branch 'master' of https://github.com/openjdk/jdk into JDK-8293781
 - add relocInfo comments for far_call/far_jump
 - modify comments
 - fix a typo
 - Clarify types of calls

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10311/files
  - new: https://git.openjdk.org/jdk/pull/10311/files/49355876..ee810dbd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10311&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10311&range=03-04

  Stats: 2297 lines in 175 files changed: 1320 ins; 472 del; 505 mod
  Patch: https://git.openjdk.org/jdk/pull/10311.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10311/head:pull/10311

PR: https://git.openjdk.org/jdk/pull/10311