ionic: add hw timestamp support files

This adds the file of code for supporting Tx and Rx hardware
timestamps and the raw clock interface, but does not yet link
it in for compiling or use.
Signed-off-by: Allen Hubbe <allenbh@pensando.io>
Signed-off-by: Shannon Nelson <snelson@pensando.io>
Signed-off-by: David S. Miller <davem@davemloft.net>