Oops, fix typo. EAN, not EAD

Oops, fix typo. EAN, not EAD

Typo turned EAN (Enriched Air Nitrox) to EAD.  Which does mean something
too, just to confuse people - but while it's still nitrox-related, it's
entirely the wrong thing (Equivalent Air Depth).  I don't think anybody
would ever care to see *that*. With computers, why would you care?

Anyway, Dirk noticed it, and suggested I just use O2% instead.  It's not
like EAN is all that readable either.

Reported-by: Dirk Hohndel <dirk@hohndel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>