emmc-image: fix echo service files "-e" is only needed in bash but not in dash, which will make service files have a "-e" garbage line. Tested: in bash and dash, verified that printf works fine Google-Bug-Id: N/A, systemd will ignore the line so no real impact Fusion-Link: fusion2 N/A platforms specific only change Change-Id: Id07d6b0a4b0041a80912be3c3120c1228205952d Signed-off-by: Yuxiao Zhang <yuxiaozhang@google.com>