Bluetooth: hci_bcm: Mandate presence of shutdown and device wake GPIO

Commit 0395ffc1 ("Bluetooth: hci_bcm: Add PM for BCM devices")
amended this driver to request a shutdown and device wake GPIO on probe,
but mandated that only one of them need to be present:

	/* Make sure at-least one of the GPIO is defined and that
	 * a name is specified for this instance
	 */
	if ((!dev->device_wakeup && !dev->shutdown) || !dev->name) {
		dev_err(&pdev->dev, "invalid platform data\n");
		return -EINVAL;
	}

However the same commit added a call to bcm_gpio_set_power() to the
->probe hook, which unconditionally accesses *both* GPIOs.  Luckily,
the resulting NULL pointer deref was never reported, suggesting there's
no machine where either GPIO is missing.

Commit 8a920568 ("Bluetooth: hci_bcm: Add (runtime)pm support to the
serdev driver") removed the check whether at least one of the GPIOs is
present without specifying a reason.

Because commit 62aaefa7 ("Bluetooth: hci_bcm: improve use of gpios
API") refactored the driver to use devm_gpiod_get_optional() instead of
devm_gpiod_get(), one is now tempted to believe that the driver doesn't
require *any* of the two GPIOs.

Which is wrong, the driver still requires both GPIOs to avoid a NULL
pointer deref.  To this end, establish the status quo ante and request
the GPIOs with devm_gpiod_get() again.  Bail out of ->probe if either
of them is missing.

Oddly enough, whereas bcm_gpio_set_power() accesses the device wake pin
unconditionally, bcm_suspend_device() and bcm_resume_device() do check
for its presence before accessing it.  Those checks are superfluous,
so remove them.

Cc: Frédéric Danis <frederic.danis.oss@gmail.com>
Cc: Loic Poulain <loic.poulain@linaro.org>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>