tsnep: Fix TSNEP_INFO_TX_TIME register define

Fixed register define is not used, but register definition shall be kept
in sync.

Fixes: 403f69bb ("tsnep: Add TSN endpoint Ethernet MAC driver")
Signed-off-by: Gerhard Engleder <gerhard@engleder-embedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>