Blackfin: punt Blackfin-specific GPIO wakeup API

This patch removes a custom GPIO wakeup API which allowed GPIOs to act
as wakeup sources, which are not configured as Interrupts.
This API is a leftover from the time before irq_wake was established.
From now on people must use enable_irq_wake(GPIO_IRQx) and the GPIO in
question needs to be configured as Interrupt.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>