sfc: Fix reporting of IPv4 full filters through ethtool

[ Upstream commit ac70b2e9a13423b5efa0178e081936ce6979aea5 ]

ETHTOOL_GRXCLSRULE returns filters for a TCP/IPv4 or UDP/IPv4 4-tuple
with source and destination swapped.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>