gpio: add gpio_add_lookup_tables() to add several tables at once

When converting legacy board to use gpiod API() there might be several
lookup tables in board file, let's provide a way to register them all at
once.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>