Blackfin arch: Cleanup and unify Blackfin IRQ and GPIO IRQ handling

 - Remove SSYNC()
 - Use irq_to_gpio where applicable
 - Remove gpio_edge_triggered bitfield, check irq_desc fields instead.
 - Remove gpio_both_edge_triggeredb bitfield, check irq_desc fields
   instead.
 - Use BITMAP and bitops on gpio_enabled
 - Preferably use 32-bit
 - Looking at the disassembly this indeed saves quite a few instructions.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>