i40e/i40evf: Add exception handling for Tx checksum

i40e/i40evf: Add exception handling for Tx checksum

Orabug: 22342532

Add exception handling to the Tx checksum path so that we can handle cases
of TSO where the frame is bad, or Tx checksum where we didn't recognize a
protocol

Drop I40E_TX_FLAGS_CSUM as it is unused, move the CHECKSUM_PARTIAL check
into the function itself so that we can decrease indent.

Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
(cherry picked from commit 529f1f652e3c3c6db6ab5a6e3a35469ddfd9575d)
Signed-off-by: Brian Maly <brian.maly@oracle.com>