[riscv-port] RFR: 8276988: riscv: Fix a register name string: lr to x5

[zhengxiaolinX]

On Thu, 11 Nov 2021 09:25:24 GMT, zhengxiaolinX <duke at openjdk.java.net> wrote:

> Hi team -
> 
> Simply fix a register name string: `lr` is `names[1]` so `names[5]` should be `x5`.
> 
> Thanks,
> Xiaolin

Seems the third checkbox needs a mark.
![image](https://user-images.githubusercontent.com/38156692/141717351-eebce4bf-9672-4f17-80f6-af30f33ba410.png)

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PR: https://git.openjdk.java.net/riscv-port/pull/2