Make sure that only the valid combinations of FCS/CRC stripping and
VLAN stripping offloads are allowed.

You cannot have FCS/CRC stripping disabled while VLAN stripping is
enabled - this breaks the correctness of the FCS/CRC.

If administrator tries to enable VLAN stripping when FCS/CRC stripping is
disabled, the request should be rejected.

If administrator tries to disable FCS/CRC stripping when VLAN stripping
is enabled, the request should be rejected if VLANs are configured. If
there is no VLAN configured, then both FCS/CRC and VLAN stripping should
be disabled.

Testing Hints:
The default settings after driver load are:
- VLAN C-Tag offloads are enabled
- VLAN S-Tag offloads are disabled
- FCS/CRC stripping is enabled

Restore the default settings before each test with the command:
ethtool -K eth0 rx-fcs off rxvlan on txvlan on rx-vlan-stag-hw-parse off
tx-vlan-stag-hw-insert off

Test 1:
Disable FCS/CRC and VLAN stripping:
ethtool -K eth0 rx-fcs on rxvlan off
Try to enable VLAN stripping:
ethtool -K eth0 rxvlan on

Expected: VLAN stripping request is rejected

Test 2:
Try to disable FCS/CRC stripping:
ethtool -K eth0 rx-fcs on

Expected: VLAN stripping is also disabled, as there are no VLAN
configured

Test 3:
Add a VLAN:
ip link add link eth0 eth0.42 type vlan id 42
ip link set eth0 up
Try to disable FCS/CRC stripping:
ethtool -K eth0 rx-fcs on

Expected: FCS/CRC stripping request is rejected
Signed-off-by: NAnatolii Gerasymenko <anatolii.gerasymenko@intel.com>
Tested-by: Gurucharan <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: NTony Nguyen <anthony.l.nguyen@intel.com>