sfc: fix IPID endianness in TSOv2

The value we read from the header is in network byte order, whereas
 EFX_POPULATE_QWORD_* takes values in host byte order (which it then
 converts to little-endian, as MCDI is little-endian).

Fixes: e9117e50 ("sfc: Firmware-Assisted TSO version 2")
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>