convert RCOutput to new virtual timer interface
cope with SDC vs SDMMC
use new SPIv3 driver. Correct clocks for SDMMCv2.
add STM32L431 support
port ChibiOS config to version 8
support SPIv3 driver model v2 on H7
use currcore in debug options
use new mmc API
disable speed optimizations in the bootloader to save a little flash
upgrade to halconf v8.4
relax constraints on QSP/flash clock.
add support for disabling QSPI reset in main firmware