it8761e_gpio: fix bug in gpio numbering

The SIO chip contains 16 possible gpio lines, not 14.  The schematic was
not read carefully.

Signed-off-by: Denis Turischev <denis@compulab.co.il>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>