system_stm32: Reset cause register must be reset!
arch.nut: Add STM32G473
stm32g4: RAM2 is better declared as CCM. Fix Typo.
stm32l4: Enable Low Power Mode when running below 2 MHz
stm32l4/flash: Change test for unaligned write.
Conf: Provide boardname as a define
stm32_spi_c: Handle transfer on devices with FIFO
stm32_spi_cb: Fix wrong SPI rate indication