Initialization problem on v0.9 Upstream board

[robertfisk]

A user reported their DIY v0.9 running 0.9r03 firmware was not working. Upstream was stuck in the CheckFirmwareMatchesHardware() function on bootup.

We determined this was due to the PC12-pullup check failing (implying that the firmware was not running on a H405 board). Bypassing the PC12 check allowed normal functionality.

We need to determine if this issue can be fixed with a delay in the PC12 check, and how much delay is required. Or whether the issue is due to a logic threshold change, in which case we probably want to find another way to confirm we are running on a H405 board.