gpiolib: split linux/gpio/driver.h out of linux/gpio.h

Almost all gpio drivers include linux/gpio/driver.h, and other
files should not rely on includes from this header.

Remove the indirect include from here and include the correct
headers directly from where they are used.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Lee Jones <lee@kernel.org>