util/ectool.c: Make sure device_name is NUL terminated
util/ectool.c: Make sure device_name is NUL terminated

BRANCH=none
BUG=none
TEST=none

Found-by: Coverity Scan #144116
Change-Id: I9ec030c1a3820af7d08c2a83e3c1f4c3ee7a3f0a
Signed-off-by: Patrick Georgi <bc411205f21846a74924ee7b489c75617ec76078@google.com>
Reviewed-on: https://chromium-review.googlesource.com/702302
Commit-Ready: Patrick Georgi <bc411205f21846a74924ee7b489c75617ec76078@chromium.org>
Tested-by: Patrick Georgi <bc411205f21846a74924ee7b489c75617ec76078@chromium.org>
Reviewed-by: Chris Ching <8c8233afb950e16b85488c94fcace43a75534f7e@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec