RFR: 8343030: RISC-V: Small assembler cleanups [v2]

[Fei Yang]

> Hi, please review this small code cleanups.
> 
> Witnessed some explicit type conversion to `address` is not necessary now.
> Also we can make use of `void la(Register Rd, const address addr)` where possible to simplify the code.
> This also adds one temporary register parameter for the `cmpptr` assembler routine.
> 
> Testing on linux-riscv64:
> - [ ] tier1 (release)

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

  Comment

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Changes:
  - all: https://git.openjdk.org/jdk/pull/21699/files
  - new: https://git.openjdk.org/jdk/pull/21699/files/001b2e27..ea73a278

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21699&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21699&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/21699.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21699/head:pull/21699

PR: https://git.openjdk.org/jdk/pull/21699