[RFA 1/3] Add usage to printf command

[Tom Tromey]

>>>>> "Alan" == Alan Hayward <Alan.Hayward@arm.com> writes:

Alan> I like the addition of a “usage”. But this will be the only command to have it.

Plenty of commands have it.

Alan> Probably not in scope for this patch series, but it would be nice for consistency
Alan> for usage statements to be added to all the commands in this file.

I can drop this patch.

Tom