Replace the old SDLOG_DIRS_MAX=3 + larger-buffer override with the
new rotation-based tuning: SDLOG_MAX_SIZE=40 caps each log file at
40 MB so a handful of recent logs fit, and SDLOG_ROTATE=95 lets logs
fill up to 95% of the 128 MB volume.
Drop the BOARD_SMALL_FLASH_LOGGING define from board_config.h; the
logger no longer keys off a per-board compile flag.
be39ec49e5