cmd: kconfig: Make ufs prompt look similar to other commands

At present the 'ufs' command prompt does not look similar like other
commands. Update it.

Signed-off-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Neha Malcom Francis <n-francis@ti.com>