User project needs reset pin

[RTimothyEdwards]

There are instances in which a user project may try to start on power up but the management SoC may not load the GPIO states until later. If the user project has not declared the GPIO defauts as needed for power up, then the user project could end up in an unrecoverable state.

The solution is to have a reset for the user project that can be applied independently of the reset to the management SoC, and which would be memory-mapped and also available in the housekeeping SPI. The program running from the management SoC could then hold the user project in reset until power supplies are reading stable and the GPIO state has been loaded.