net: Support network packet checksum calc offloading

Create infrastructure that allows ethernet device driver to tell
if it supports network packet checksum offloading. This applies only
to IPv4, UDP or TCP checksums. The driver can enable/disable checksum
offloading separately for Tx and Rx network packets.

If the device (ethernet in this case) can calculate the network
packet checksum for IPv4, UDP or TCP, then do not calculate the
corresponding checksum by the stack itself.

Fixes #2987

Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>