ata: palmld: Convert to GPIO descriptors

Instead of passing GPIO numbers directly to the PalmLD
ATA driver, pass GPIO descriptors from the board file and
handle these in the driver.

Cc: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>