We have already a global array of possible GPIO suffixes. Use it here instead
of another copy of them.

Unfortunately this will not reduce the memory footprint, though allows to easy
maintain list in only one place.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>