PCI: apple: Do not leak reset GPIO on unbind/unload/error

PCI: apple: Do not leak reset GPIO on unbind/unload/error

The driver allocates reset GPIO in apple_pcie_setup_port() but neither
releases the resource, nor uses devm API to have it released
automatically.

Let's fix this by switching to devm API. While at it let's use generic
devm_fwnode_gpiod_get() instead of OF-specific gpiod_get_from_of_node()
- this will allow us top stop exporting the latter down the road.

Link: https://lore.kernel.org/r/YxatO5OaI2RpxQ2M@google.com
Fixes: 1e33888fbe44 ("PCI: apple: Add initial hardware bring-up")
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Hector Martin <marcan@marcan.st>
Acked-by: Marc Zyngier <maz@kernel.org>