Bluetooth: Depend on rather than select GPIOLIB

Commit 27378f4c ("Bluetooth: Avoid WARN splat due to missing
GPIOLIB") amended Kconfig to select GPIOLIB if BT_HCIUART_NOKIA,
BT_HCIUART_INTEL or BT_HCIUART_BCM is enabled since all three drivers
require it to function.

The diagnosis was correct but the treatment was not.  As stated in
Documentation/gpio/consumer.txt:

    Guidelines for GPIOs consumers
    ==============================

    Drivers that can't work without standard GPIO calls should have
    Kconfig entries that depend on GPIOLIB.
                         ^^^^^^^^^
Fix it.

Reported-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>