Only update /etc/default/grub in OEM kernel update instructions if 'quiet splash' are not included

[rathboma]

Don't update this line if quiet splash is present.

Fixes https://community.frame.work/t/amd-oem-kernel-update-procedure-breaks-hibernate-by-updating-grub-cmdline-linux-default-in-etc-default-grub/44726

This:

1. Checks if quiet splash is included on the defaults line
2. Only blitzes the line if they are not present
3. Leaves the line as-is if quiet splash are present.

Why?

• If a user has enabled hibernation, this will not remove their hibernate configs from this line and break hibernation (so long as they have quiet splash)

Improvements? It might be good to be more sophisticated with this check and warn users if something will be overwritten.

[ctsdownloads]

I am keeping this open, I think there is real merit to it. Going to try and make some time to put together some thoughts on how to be address this. Your pull request in on point for folks using hibernation, etc. I am putting a pin this, but keeping it open to circle back.

[ctsdownloads]

Patched added. Thanks for your help.