console: Fix console buffer overrun

When CONFIG_SYS_CBSIZE equals MAX_CMDBUF_SIZE, a command string of
maximum length will overwrite part of the history buffer, causing the
board to die. Expand the console_buffer and hist_lines buffer by one
character each to hold the missing NULL char.

Signed-off-by: John Schmoller <jschmoller@xes-inc.com>