Configurable RAM sizes for V20x, V30x

[maxgerhardt]

The linker script

https://github.com/cnlohr/ch32v003fun/blob/6c14912e79adf9097d46c3f4688da3b567d64d6c/ch32v003fun/ch32v003fun.ld#L31-L40

for V30x only gives the "256K Flash + 64K RAM" and "128K Flash + 32K RAM" option. This is however wrong: The 128K Flash option doesn't exist naturally. The options for 30x are

And for 20x

Through invocation of the blackest dark magic I've ever seen, flash cells become RAM cells, and their sum is a constant.

Also see https://github.com/Community-PIO-CH32V/platform-ch32v/issues/20 and https://github.com/Community-PIO-CH32V/platform-ch32v/issues/17#issuecomment-1446040078

What I'm specifically saying is that I think the linker script and Makefile is wrong by deducing the "one right" memory sizes only through the chip's name / package name, when in fact, some chips are more freely configurable.