To avoid recursive dependencies on GPIOLIB when 'imply IIO' is requested
with other drivers we should switch GPIOLIB to an imply.

This isn't the most ideal solution but avoids modifiying the Kconfig for
other drivers, and only requires a singular IS_REACHABLE(CONFIG_GPIOLIB)
check.
Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>