avr32: do away with ARCH_REQUIRE_GPIOLIB

Replace "select ARCH_REQUIRE_GPIOLIB" with "select GPIOLIB"
as this can now be selected directly.

Cc: Michael Büsch <m@bues.ch>
Cc: Haavard Skinnemoen <hskinnemoen@gmail.com>
Acked-by: Acked-by: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>