RFR: 8315931: RISC-V: xxxMaxVectorTestsSmokeTest fails when using RVV

[Gui Cao]

Hi, This patch fixes an error when qemu enabled the parameter rvv_ta_all_1s=true. The reason for the error is that the number of 1s fetched here may be smaller than Matcher::vector_length(this), and so the wrong vl to the Matcher::vector_length(this) is mistaken for a tail[1]. is mistaken for the tail data and is set to 1.

### Testing:
qemu with UseRVV:
- [x] test/jdk/jdk/incubator/vector (fastdebug)

qemu with rvv_ta_all_1s=true and UseRVV:
- [x] test/jdk/jdk/incubator/vector (fastdebug)

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

Commit messages:
 - 8315931: RISC-V: xxxMaxVectorTestsSmokeTest fails when using RVV

Changes: https://git.openjdk.org/jdk/pull/15680/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15680&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315931
  Stats: 27 lines in 1 file changed: 8 ins; 8 del; 11 mod
  Patch: https://git.openjdk.org/jdk/pull/15680.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15680/head:pull/15680

PR: https://git.openjdk.org/jdk/pull/15680