device/pciexp: Add hot-plug capable helper function

Add and use a new helper function to determine if a device is
1) a PCIe device
2) it's mark hot-plug capable

Change-Id: I61cc013844024b43808cd2f054310cb6676ba69e
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/84792
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Shuo Liu <shuo.liu@intel.com>

src/include/device/pciexp.h

@@ -45,6 +45,8 @@ static inline bool pciexp_is_downstream_port(int type)
 	       type == PCI_EXP_TYPE_PCIE_BRIDGE;
 }
 
+bool pciexp_dev_is_slot_hot_plug_cap(struct device *dev);
+
 struct device *pcie_find_dsn(const uint64_t serial, const uint16_t vid,
 	struct device *from);