blackfin: gpio: Remove none gpio lib code.

- Remove non gpio lib code from blackfin architecture.
- Limit the lagecy blackfin gpio driver to bf5xx processors only.
- Remove unused definition of the pint power functions.

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>