RFR: 8371869: RISC-V: too many warnings when build on BPI-F3 SBC

[Fei Yang]

Hi, please consider this riscv-specific change.

I witnessed 400+ warning messages when doing a native build on BPI-F3 SBC running kernel 6.6.63.
`OpenJDK 64-Bit Server VM warning: Cannot enable UseZvfh, it's missing dependent extension(s) v (disabled), Zfh (enabled)`

The warning messages indicate that we won't auto-enable extensions like `Zvfh` due to lack of vector support on old kernels.
I think these warning messages could be confusing to people. It might be more reasonable to just log these messages.
This also unifies the way of logging prefering `log_info`. It doesn't seem necessary to me to use `log_debug` in this case.

After this change, the log looks like:

$ java -Xlog:all -version

......
[0.011s][info][os         ] Linux kernels before 6.8.5 (current 6.6.63) have a known bug when using Vector and signals.
[0.011s][info][os         ] Vector not enabled automatically via hwprobe, but can be turned on with -XX:+UseRVV.
[0.011s][info][os,cpu     ] Enabled RV64 feature "a"
[0.011s][info][os,cpu     ] Enabled RV64 feature "c"
[0.011s][info][os,cpu     ] Enabled RV64 feature "d"
[0.011s][info][os,cpu     ] Enabled RV64 feature "f"
[0.011s][info][os,cpu     ] Enabled RV64 feature "i"
[0.011s][info][os,cpu     ] Enabled RV64 feature "m"
[0.011s][info][os,cpu     ] Enabled RV64 feature "Zba"
[0.011s][info][os,cpu     ] Enabled RV64 feature "Zbb"
[0.011s][info][os,cpu     ] Enabled RV64 feature "Zbs"
[0.011s][info][os,cpu     ] Enabled RV64 feature "Zfh"
[0.011s][info][os,cpu     ] Enabled RV64 feature "Zfhmin"
[0.011s][info][os,cpu     ] Disabled RV64 feature "Zvfh" (missing dependent extension(s): v (disabled), Zfh (enabled))
[0.011s][info][os,cpu     ] Enabled RV64 feature "marchid" (-9223372035378380799)
[0.011s][info][os,cpu     ] Enabled RV64 feature "mimpid" (1152921505839391232)
[0.011s][info][os,cpu     ] Enabled RV64 feature "mvendorid" (1808)
[0.011s][info][os,cpu     ] Enabled RV64 feature "satp_mode" (39)
[0.011s][info][os,cpu     ] Enabled RV64 feature "unaligned_scalar" (3)
[0.011s][info][os,cpu     ] Enabled RV64 feature "zicboz_block_size" (64)
[0.011s][info][os,cpu     ] Zifencei not found, required by Linux, enabling.
[0.012s][info][os,cpu     ] CPU: total 8 (initial active 8) spacemit,x60 rv64 rva rvc rvd rvf rvi rvm zba zbb zbs zfh zfhmin
......

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

Commit messages:
 - 8371869: RISC-V: too many warnings when build on BPI-F3 SBC

Changes: https://git.openjdk.org/jdk/pull/28340/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28340&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371869
  Stats: 36 lines in 2 files changed: 27 ins; 6 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/28340.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28340/head:pull/28340

PR: https://git.openjdk.org/jdk/pull/28340