powerpc/85xx: typo in dts: "interupt" (four devices)

These lines were inoperative for four years, which puts some doubt into
their importance, and it's possible the fixed version will regress, but
at the very least they should be removed instead.

Signed-off-by: Adam Borowski <kilobyte@angband.pl>
Signed-off-by: Scott Wood <scottwood@freescale.com>