staging: mt7621-gpio: fix some warnings because of lines exceeded 80 characters

This patch silence some complains of checkpatch script because
of the use of long lines.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>