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

[Fei Yang]

On Thu, 18 Nov 2021 02:52:17 GMT, Yanhong Zhu <yzhu at openjdk.org> wrote:

> 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. 
> Hotspot tier1 tests pass on QEMU.

Nice cleanup. Looks good.

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Marked as reviewed by fyang (Lead).

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