cli: compile history code if and only if history config is selected

This commit allows user to determine whether to have history recording
in command-line. Previously to this commit, the CMD_HISTORY only sets
the compiling of cmd/history.c, and the history code in cli_readline.c
is always compiled and will take a lot of space to store history even if
we say N to CMD_HISTORY.

Signed-off-by: Hanyuan Zhao <hanyuan-z@qq.com>