[AVR32] gpio_*_cansleep() fix

The AVR32 <asm/gpio.h> was missing the gpio_*_cansleep() calls,
breaking compilation for some code using them.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>