cmd: efidebug: Add missing \n at the end of message

Currently message is not intended that prompt end up at the end of debug
line. For example like this:

DFU alt info setting: done
DFU entities configuration failed!
(partition table does not match dfu_alt_info?)
Firmware update failed: <NULL>
Cannot handle a capsule at 10000000Zynq>

Signed-off-by: Michal Simek <michal.simek@amd.com>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>