zephyr: i2c_mock emulator: add explicit label property
zephyr: i2c_mock emulator: add explicit label property

The i2c_mock emulator and tests currently require the label property.
Override the deprecated attribute from the base.yaml.

BUG=b:239165779
BRANCH=none
TEST=./twister --clobber

Signed-off-by: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>
Change-Id: Iae40d695a6ae0e92a448a6a0b123d9cb3f1b1899
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3852903
Reviewed-by: Jeremy Bettis <4df7b5147fee087dca33c181f288ee7dbf56e022@chromium.org>
Reviewed-by: Fabio Baltieri <1c55e39c05d9ab42261288cf330256b2af6ba179@google.com>

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