selftests: hw-net: rss-input-xfrm: try to enable the xfrm at the start

selftests: hw-net: rss-input-xfrm: try to enable the xfrm at the start

The test currently SKIPs if the symmetric RSS xfrm is not enabled
by default. This leads to spurious SKIPs in the Intel CI reporting
results to NIPA.

Testing on CX7:

 # ./drivers/net/hw/rss_input_xfrm.py
  TAP version 13
  1..2
  ok 1 rss_input_xfrm.test_rss_input_xfrm_ipv4 # SKIP Test requires IPv4 connectivity
  # Sym input xfrm already enabled: {'sym-or-xor'}
  ok 2 rss_input_xfrm.test_rss_input_xfrm_ipv6
  # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:1 error:0

 # ethtool -X eth0 xfrm none

 # ./drivers/net/hw/rss_input_xfrm.py
  TAP version 13
  1..2
  ok 1 rss_input_xfrm.test_rss_input_xfrm_ipv4 # SKIP Test requires IPv4 connectivity
  # Sym input xfrm configured: {'sym-or-xor'}
  ok 2 rss_input_xfrm.test_rss_input_xfrm_ipv6
  # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:1 error:0

Link: https://patch.msgid.link/20260104184600.795280-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>