ACPI: dock: fix "sibiling" typo

Crossword clues as haikus:

	Snakes from the same brood
	fighting Jackson on a plane?
	sibilant siblings

I guess Will Shortz's job is still secure.

Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Len Brown <len.brown@intel.com>