net: stmmac: Add check for taprio basetime configuration

Adds a boundary check to prevent negative basetime input from user
while configuring taprio.

Signed-off-by: Michael Sit Wei Hong <michael.wei.hong.sit@intel.com>
Signed-off-by: Lai Peter Jun Ann <jun.ann.lai@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>