gpio: Fix loose spelling

Literally.

I expect "lose" was meant here, rather than "loose", though you could feasibly
use a somewhat uncommon definition of "loose" to mean what would be meant by
"lose": "Loose the hounds" for instance, as in "Release the hounds".
Substituting in "value" for "hounds" gives "release the value", and makes some
sense, but futher substituting back to loose gives "loose the value" which
overall just seems a bit anachronistic.

Instead, use modern, pragmatic English and save a character.

Cc: Russell Currey <ruscur@russell.cc>
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>