submodule(ready-to-run): bump nemu ref

[NewPaulWalker]

• NEMU commit: refactor(csrrw): rewrite csr read/write using switch-case instead of multiple if-else. NEMU#573
• NEMU configs:
  • riscv64-xs-ref_defconfig
  • riscv64-dual-xs-ref_defconfig

Including:

• refactor(csrrw): rewrite csr read/write using switch-case instead of multiple if-else.

[NewPaulWalker]

I used a commit from a pull request in the ready-to-run submodule that hasn't been merged into the master branch yet for testing.
If all tests except for the check submodule test pass, I'll merge the pull request for NEMU, update ready-to-run, and then update the current pull request again to ensure it passes all CI tests.