gpio-langwell: use managed functions pcim_* and devm_*

This makes the error handling much more simpler than open-coding everything and
in addition makes the probe function smaller an tidier.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: David Cohen <david.a.cohen@intel.com>
[Rebased on the platform-data set to NULL removal patch]
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>