[riscv-port] RFR: 8277167: riscv: Remove unnecessary register declaration for lr

[Yanhong Zhu]

Currently, there are two register declarations for both 'ra' and 'lr' on riscv port. But they refer to the same register x1. Since 'ra' is the ABI name for register x1, we should keep register declaration for 'ra' and remove register declaration for 'lr' in order to avoid possible confusion.

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Commit messages:
 - 8277167: riscv: Remove unnecessary register declaration for lr

Changes: https://git.openjdk.java.net/riscv-port/pull/6/files
 Webrev: https://webrevs.openjdk.java.net/?repo=riscv-port&pr=6&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277167
  Stats: 122 lines in 19 files changed: 1 ins; 4 del; 117 mod
  Patch: https://git.openjdk.java.net/riscv-port/pull/6.diff
  Fetch: git fetch https://git.openjdk.java.net/riscv-port pull/6/head:pull/6

PR: https://git.openjdk.java.net/riscv-port/pull/6