net: bnxt: Add boilerplate GSO code

net: bnxt: Add boilerplate GSO code

Add bnxt_gso.c and bnxt_gso.h with a stub bnxt_sw_udp_gso_xmit()
function, SW USO constants (BNXT_SW_USO_MAX_SEGS,
BNXT_SW_USO_MAX_DESCS), and the is_sw_gso field in bnxt_sw_tx_bd
with BNXT_SW_GSO_MID/LAST markers.

The full SW USO implementation will be added in a future commit.

Suggested-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Joe Damato <joe@dama.to>
Link: https://patch.msgid.link/20260408230607.2019402-7-joe@dama.to
Signed-off-by: Jakub Kicinski <kuba@kernel.org>