dt-bindings: misc: pci1de4,1: add required reg property for endpoint

dt-bindings: misc: pci1de4,1: add required reg property for endpoint

The PCI subsystem links an endpoint Device Tree node to its corresponding
pci_dev structure only if the Bus/Device/Function (BDF) encoded in the
'reg' property matches the actual hardware topology.

Add the 'reg' property and mark it as required to ensure proper binding
between the device_node and the pci_dev.

Update the example to reflect this requirement.

Signed-off-by: Andrea della Porta <andrea.porta@suse.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/b58bfcd957b2270fcf932d463f2db534b2ae1a6d.1766077285.git.andrea.porta@suse.com
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>