Bluetooth: increment TX timestamping tskey always for stream sockets

Documentation/networking/timestamping.rst implies TX timestamping OPT_ID
tskey increments for each sendmsg.  In practice: TCP socket increments
it for all sendmsg, timestamping on or off, but UDP only when
timestamping is on. The user-visible counter resets when OPT_ID is
turned on, so difference can be seen only if timestamping is enabled for
some packets only (eg. via SO_TIMESTAMPING CMSG).

Fix BT sockets to work in the same way: stream sockets increment tskey
for all sendmsg (seqpacket already increment for timestamped only).

Fixes: 134f4b39 ("Bluetooth: add support for skb TX SND/COMPLETION timestamping")
Signed-off-by: Pauli Virtanen <pav@iki.fi>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>