Update ipod_touch_fmss.c

[zoe-vb]

fix issue where boot arguments were not actually updating when recompiling qemu; this became a huge nuisance and I spent some time trying to track down why only to find out that the string wasn't a constant and it should have been.

[github-actions]

Thank you for your interest in the QEMU project.

This repository is a read-only mirror of the project's repostories hosted
on https://gitlab.com/qemu-project/qemu.git.
The project does not process merge requests filed on GitHub.

QEMU welcomes contributions of code (either fixing bugs or adding new
functionality). However, we get a lot of patches, and so we have some
guidelines about contributing on the project website:
https://www.qemu.org/contribute/

[devos50]

Oh I did notice some issues with that before (changes not being applied) but didn't think it would be caused by this. Thanks!