The driver always registers pin configurations in device tree. This can
cause some inconvenience to users, as pin configurations in the base
device tree cannot be disabled in the device tree overlay, even when the
relevant devices are not used.

Ignore disabled pin configuration nodes in device tree.

Fixes: 447976ab ("pinctrl: starfive: Add StarFive JH7110 sys controller driver")
Cc:  <stable@vger.kernel.org>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Link: https://lore.kernel.org/r/fd8bf044799ae50a6291ae150ef87b4f1923cacb.1701422582.git.namcao@linutronix.deSigned-off-by: Linus Walleij <linus.walleij@linaro.org>