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
this zeros-watchdog was caused by a SPI DMA error on STM32F405:
https://discuss.ardupilot.org/t/crash-with-4-2-0-beta-and-4-3-0-daily-bdshot/83297
we had incorrectly left these internal errors enabled when asserts
were not enabled. That led to a osalSysHalt()
without these we get an spi_fail internal error, caught by the
SPIDevice code
