RFR: 8319960: RISC-V: compiler/intrinsics/TestInteger/LongUnsignedDivMod.java failed with "counts: Graph contains wrong number of nodes"

[Hamlin Li]

Hi,
Can you review this patch to fix the test failure in compiler/intrinsics/TestInteger/LongUnsignedDivMod.java?
The reason of failure is that, `UDivModI` is only supplied on x86_64.ad, so it can not find this node on riscv.
Fix is to apply the check only on x64.
Thanks!


## Test
To reproduce the issue, 

jtreg -timeout:10 -retain -v1 -conc:32 -nr -javaoptions:"" -testjdk:build/linux-riscv64-server-fastdebug/images/jdk/ ./test/hotspot/jtreg/compiler/intrinsics/

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Commit messages:
 - Initial commit

Changes: https://git.openjdk.org/jdk/pull/16630/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16630&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319960
  Stats: 6 lines in 2 files changed: 2 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/16630.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16630/head:pull/16630

PR: https://git.openjdk.org/jdk/pull/16630