selftests: drv-net: tso: don't touch dangerous feature bits

selftests: drv-net: tso: don't touch dangerous feature bits

query_nic_features() detects which offloads depend on tx-gso-partial
by enabling everything, turning tx-gso-partial off, and seeing which
active features drop out. Enabling all hw features is dangerous:
we may end up enabling rx-fcs and loopback for example. For the
ice driver we end up getting into problems with feature dependencies
so the cleanup isn't successful either, and the test exits with
rx-fcs and loopback enabled.

Scope the feature probing just to segmentation bits.

Fixes: 266b835e5e84 ("selftests: drv-net: tso: enable test cases based on hw_features")
Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Reviewed-by: Daniel Zahka <daniel.zahka@gmail.com>
Link: https://patch.msgid.link/20260629233923.2151144-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>