RFR: 8294086: RISC-V: Cleanup InstructionMark usages in the backend

[Feilong Jiang]

On Wed, 21 Sep 2022 03:50:22 GMT, Xiaolin Zheng <xlinzheng at openjdk.org> wrote:

> This is a trivial cleanup of dummy `InstructionMark` usages in the RISC-V backend. There are no more `InstructionMark` usages in the backend now.
> 
> Tested hotspot tier1 and tier2 on Qemu.

Nice cleanup, thanks!

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

Marked as reviewed by fjiang (Author).

PR: https://git.openjdk.org/jdk/pull/10369