add missing SINIT warning

[adrelanos]

In case it is forgotten or in case file names get changed by upstream give the user a hint.

Untested.

//cc @rustybird

[rustybird]

Good idea, but is the message visible in practice or does Xen startup clear the screen too fast before it can be noticed?

[adrelanos]

It's true. Hard to notice without further debugging (disabling splash screens). However, I like having this message in grub.cfg - so when reviewing the file it can be easily spot. I like hints.

Or can we add a delay so this can be read?

[rustybird]

Or can we add a delay so this can be read?

That, or wait for a key press etc. Whatever is the conventional way in GRUB land, I guess. :)