Load the M4 firmware to configure DDR PHY
Related epic: https://source.puri.sm/Librem5/use-cases/issues/108, https://source.puri.sm/Librem5/use-cases/issues/7
This code will be responsible for loading the m4 binary into TCRAM and then executing it. The m4 code configures the DDR PHY an will need to be configured to match the Librem 5 phone hardware. This is currently not an issue for the devkit.