RFR: 8332615: RISC-V: Support vector unsigned comparison instructions for machines with RVV

[Gui Cao]

Hi, I noticed the following warning in the Opto JIT Code for the Vector API in the `test/jdk/jdk/incubator/vector/Int256VectorTests.java: UNSIGNED_LTInt256VectorTests` test:

  ** not supported: unsigned comparison op=comp/1 vlen=8 etype=int ismask=usestore
``` 
After this Patch, We supports vector unsigned comparison instructions, the test passes normally and generates the Opto JIT Code such as:

23e     B46: #  out( B48 B47 ) <- in( B25 B45 ) Loop( B46-B45 ) Freq: 955.829
23e     addw  R24, R29, zr  #@convI2L_reg_reg
242     slli  R30, R24, (#2 & 0x3f) #@lShiftL_reg_imm
246     add R17, R8, R30  # ptr, #@addP_reg_reg
24a     add R19, R9, R30  # ptr, #@addP_reg_reg
24e     addi  R30, R17, #16 # ptr, #@addP_reg_imm
252     addi  R31, R19, #16 # ptr, #@addP_reg_imm
256     loadV V1, [R30] # vector (rvv)
25e     loadV V2, [R31] # vector (rvv)
266     vmaskcmp V0, V1, V2, #19
272     vmask_tolong R20, V0
280     vstoremask V1, V0 # elem size is #4 byte[s]
28c     lw  R31, [R17, #16] # int, #@loadI
290     lw  R11, [R19, #16] # int, #@loadI
294     andi  R10, R20, #1  #@andL_reg_imm
298     bne  R10, zr, B48 #@cmpL_reg_imm0_branch  P=0.669978 C=14596.000000

### Testing:
qemu 8.1.50 with UseRVV:
- [ ] Run tier1-3 tests (release)
- [x] Run test/jdk/jdk/incubator/vector (fastdebug)

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

Commit messages:
 - 8332615: RISC-V: Enable vector unsigned comparison instructions for machines with RVV

Changes: https://git.openjdk.org/jdk/pull/19328/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19328&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8332615
  Stats: 6 lines in 2 files changed: 4 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/19328.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19328/head:pull/19328

PR: https://git.openjdk.org/jdk/pull/19328