sun: Add SPDX license tags to Sun network drivers

Add the appropriate SPDX license tags to the Sun network drivers
as outlined in Documentation/process/license-rules.rst.

Signed-off-by: Shannon Nelson <shannon.nelson@oracle.com>
Reviewed-by: Zhu Yanjun <yanjun.zhu@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>