When 'CPU' is defined, the CPU Makefile.features is included by the build system in the main Makefile.features. No need to do it manually anymore.
- Created new `bluepill-128kib` as 128KiB version of the `bluepill` - Created new `blackpill-128kib` as 128KiB version of the `blackpill` - Updated `openocd.cfg` to allow flashing 128KiB of ROM