pciexp_device: Propagate above-4G flag to all hotplug devices

The `IORESOURCE_ABOVE_4G` flag was only explicitly set for our dummy
device that reserves resources behind a hotplug port. The current re-
source allocator implicitly extends this to all devices below the port,
including real ones. Let's make that explicit, so future changes to the
allocator can't break this rule.

Change-Id: Id4c90b60682cf5c8949cde25362d286625b3e953
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/66719
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>

src/include/device/device.h

@@ -128,6 +128,7 @@ struct device {
 	unsigned int    hidden : 1;
 	/* set if this device is used even in minimum PCI cases */
 	unsigned int    mandatory : 1;
+	unsigned int	hotplug_port : 1;
 	u8 command;
 	uint16_t hotplug_buses; /* Number of hotplug buses to allocate */
 
@@ -207,6 +208,9 @@ void add_more_links(struct device *dev, unsigned int total_links);
 bool is_dev_enabled(const struct device *const dev);
 bool is_devfn_enabled(unsigned int devfn);
 
+/* Returns whether there is a hotplug port on the path to the given device. */
+extern bool dev_path_hotplug(const struct device *);
+
 /* Option ROM helper functions */
 void run_bios(struct device *dev, unsigned long addr);