BugLink: http://bugs.launchpad.net/bugs/1553179

commit 2f538c01 upstream.

Occasionally the setup function will be called multiple times. Only request
the gpio the first time otherwise -EBUSY will occur on subsequent calls to
setup.
Reported-by: Joseph Bell <joe@iachieved.it>
Signed-off-by: Michael Welling <mwelling@ieee.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>