TCPCIv2: Send i2c stop bit after control messages
TCPCIv2: Send i2c stop bit after control messages

Control messages contain no data, so the i2cxfer call to transmit the
message data and stop bit were being skipped.  This change sends the
stop bit when the message contains only the header.

BRANCH=None
BUG=None
TEST=waddledoo sends control messages successfully to Apple 3-in-1
dongle

Change-Id: Iaa6a55cf6279265ed26859925d16cb05baaa0a23
Signed-off-by: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2036813
Reviewed-by: Aseda Aboagye <12c9b286316a940fd31c24070da5ab64cdd4d0e7@chromium.org>

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