ipxe version update is dangerous

[majst01]

See:

• MFS set too low on Intel 40GBE? ipxe/ipxe#987
• Newer ipxe sets the MFS of intel cards to low #17

So before update the ipxe commit sha, this must be thoroughly tested id MFS is still 1536 after booting the machine image.

[vknabel]

Is there anything to do here? Do we lack documentation? E.g. in the README development section?

[majst01]

Someone could let AI write a good documentation regarding this issue into the README.md