ARM: stm32: Add MAC address readout from fuses on DH STM32MP1 DHSOM

ARM: stm32: Add MAC address readout from fuses on DH STM32MP1 DHSOM

Add support for reading out the MAC address from SoC fuses on DH STM32MP1 DHSOM.
The DH STM32MP1 DHSOM may contain external ethernet MACs, which benefit from the
MAC address stored in SoC fuses as well, handle those consistently. This however
means the architecture setup_mac_address() cannot be used and instead a simpler
local fuse read out is implemented in the board file.

Signed-off-by: Marek Vasut <marek.vasut@mailbox.org>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>