RTC support for STM32G474

[viperidae]

Looks like there is no RTC implementation for STM32G4 series chips.

It is very similar to the RTC in the STM32L4 series.

[n0stalgic]

Hi @viperidae , are you handling this? otherwise I can work on this. thanks!

[viperidae]

I wasn't planning on it @n0stalgic . My C is a quite rusty.

[viperidae]

Sort of related, but I noticed there is no LPUART1 defined for the G4 series either.
LPUART1_BASE is defined in g4/memorymap.h but there is LPUART1 defined in g4/uart.h

g0/uart.h does have "#define LPUART1 LPUART1_BASE"