igc: Add checking for basetime less than zero

Using the tc qdisc command, the user can set basetime to any value.
Checking should be done on the driver's side to prevent registering
basetime values that are less than zero.

Fixes: ec50a9d4

 ("igc: Add support for taprio offloading")
Signed-off-by: Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@intel.com>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>