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 takes better advantage of the new UART code. Log download over
USB gets to 730 kbyte/s. For comparison, with the 4.0 code on the same
H7 we get about 300 kbyte/s
this gains about 20k of RAM, and has almost no impact on log download
speed at 921600 on a F427. The improved threading means we can afford
to have smaller buffers
this uses the ChibiOS system timer instead of a separate GPT timer for
the core ChibiOS timer. The advantage is it saves us a timer, plus it
changes ChibiOS to use a 1MHz clock on its timer, which gives us
higher resolution for delays.
This has a remarkable effect on timing jitter, reducing it greatly
