blackfin: Fix local <asm/gpio.h> includes

blackfin: Fix local <asm/gpio.h> includes

When making the pin control submenu globally visible, all kinds
of oddities appear, in blackfin a few files were #including
<linux/gpio.h> and relying on that to pull in <asm/gpio.h>.

This was not working when pin control but not GPIOLIB was
selected resulting in a breakage in allmodconfig. The code these
files were using was still there and defined in <asm/gpio.h>
just not pulle in from just including <linux/gpio.h>

Simply add the required includes explicitly in the blackfin
kernel core and everything compiles fine.

Delete the use of the incorrect <linux/gpio.h> where possible.

Add stubs to <asm/gpio.h> for the functions called from PM:
these should probably also depend on !PINCTRL but since the
global CONFIG_PM symbol is used to compile PM support,
we need some more intrusive thing here, to be tested by
Blackfin maintainers.

Cc: Steven Miao <realmz6@gmail.com>
Cc: Huanhuan Feng <huanhuan.feng@analog.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>