[riscv-port-jdk17u:riscv-port] RFR: 8304293: RISC-V: JDK-8276799 missed atomic intrinsic support for C1

[Gui Cao]

Please review this backport to riscv-port-jdk17u.
Backport of [JDK-8304293](https://bugs.openjdk.org/browse/JDK-8304293).
Let me show the IR changes before and after the modification:
`java -Xcomp -XX:TieredStopAtLevel=1 -XX:+PrintIR -version > C1.log`

before:

B3 (V) [33, 49] dom B1 pred: B1
empty stack
inlining depth 0
__bci__use__tid____instr____________________________________
  33   1    a35    <instance 0x00000040c003c3b8 klass=java/util/concurrent/atomic/AtomicLong>
. 8    0    l42    a25.invokespecial(a35, l27, l4)
                   jdk/internal/misc/Unsafe.getAndAddLong(Ljava/lang/Object;JJ)J
  41   1    a46    <instance 0x00000040c003c3c0 klass=java/util/concurrent/atomic/AtomicLong>
  7    1    l53    1L
. 8    0    l54    a25.invokespecial(a46, l27, l53)
                   jdk/internal/misc/Unsafe.getAndAddLong(Ljava/lang/Object;JJ)J
. 49   0    i61    ireturn i29


after:

B3 (V) [33, 49] dom B1 pred: B1
empty stack
inlining depth 0
__bci__use__tid____instr____________________________________
  33   1    a35    <instance 0x00000040c003c3b8 klass=java/util/concurrent/atomic/AtomicLong>
. 8    0    l42    UnsafeGetAndSetObject (add).(a35, l27, value l4)
  41   1    a46    <instance 0x00000040c003c3c0 klass=java/util/concurrent/atomic/AtomicLong>
  7    1    l53    1L
. 8    0    l54    UnsafeGetAndSetObject (add).(a46, l27, value l53)
. 49   0    i61    ireturn i29


Testing:

Tier1 passed without new failure on unmacthed (release).

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

Commit messages:
 - backport 8304293: RISC-V: JDK-8276799 missed atomic intrinsic support for C1

Changes: https://git.openjdk.org/riscv-port-jdk17u/pull/19/files
 Webrev: https://webrevs.openjdk.org/?repo=riscv-port-jdk17u&pr=19&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8304293
  Stats: 6 lines in 1 file changed: 6 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/riscv-port-jdk17u/pull/19.diff
  Fetch: git fetch https://git.openjdk.org/riscv-port-jdk17u.git pull/19/head:pull/19

PR: https://git.openjdk.org/riscv-port-jdk17u/pull/19