dt-bindings: net: Add Broadcom BCM4377 family PCIe Bluetooth

These chips are combined Wi-Fi/Bluetooth radios which expose a
PCI subfunction for the Bluetooth part.
They are found in Apple machines such as the x86 models with the T2
chip or the arm64 models with the M1 or M2 chips.

Signed-off-by: Sven Peter <sven@svenpeter.dev>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>