[Blackfin] arch: hook up set_irq_wake in Blackfin's irq code

 - Add support for irq_wake on system and gpio interrupts
 - Remove outdated kernel options
 - Add option to select default PM mode
 - Fix various places where SIC_IWRx was only handled partially

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>