RFR: 8319440: RISC-V: remove register keyword from read_csr

Tue Nov 21 16:25:12 UTC 2023

Hello everyone! I removed the `register` keyword from `read_csr` function, which is used to check CPU vector length. Inside QEMU with RVV I see that the behavior is the same as with `register`. Furthermore, inside GDB I see that register used for `csrr vlenb` is `a0` with and without `register` keyword. With this fix `make hotspot` with latest clang used succeeded without any warnings.

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

Commit messages:
 - 8319440: RISC-V: remove register keyword from read_csr

Changes: https://git.openjdk.org/jdk/pull/16768/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16768&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319440
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16768.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16768/head:pull/16768

PR: https://git.openjdk.org/jdk/pull/16768