net/ice/base: improve GTPU extend header handle

net/ice/base: improve GTPU extend header handle

A GTPU header can stack with a extend header or not, while
current implementation does not allow HDR bit sets like below:

ICE_FLOW_SEG_HDR_GTPU_IP | ICE_FLOW_SEG_HDR_GTPU_EH
ICE_FLOW_SEG_HDR_GTPU_IP | ICE_FLOW_SEG_HDR_GTPU_UP
ICE_FLOW_SEG_HDR_GTPU_IP | ICE_FLOW_SEG_HDR_GTPU_DWN

Which is not convenient for upper layer flow parser to
generate correct HDR bit.

but it could be if we have below assumptions:

ICE_FLOW_SEG_HDR_GTPU_DWN -- for GTPU with extend header down link
ICE_FLOW_SEG_HDR_GTPU_UP  -- for GTPU with extend header up link
ICE_FLOW_SEG_HDR_GTPU_EH  -- for GTPU with any extend header
ICE_FLOW_SEG_HDR_GTPU_IP  -- for any GTPU header, but when it combined
                             with any above it downgrade to a dummy one.

And handle from specific case to generic case will hit all the cases
as expected.

if else (hdr & ICE_FLOW_SEG_HDR_GTPU_DWN) {
...
} else if (hdr & ICE_FLOW_SEG_HDR_GTPU_UP) {
...
} else if (hdr & ICE_FLOW_SEG_HDR_GTPU_EH) {
...
} else if (hdr & ICE_FLOW_SEG_HDR_GTPU_IP {
...
}

Signed-off-by: Qi Zhang <qi.z.zhang@intel.com>
Signed-off-by: Paul M Stillwell Jr <paul.m.stillwell.jr@intel.com>
Acked-by: Qiming Yang <qiming.yang@intel.com>