RDMA/bnxt_re: Fix missing error handling for tx_queue

RDMA/bnxt_re: Fix missing error handling for tx_queue

bnxt_re_fill_gen0_ext0() did not return an error when
attempting to modify CMDQ_MODIFY_ROCE_CC_MODIFY_MASK_TX_QUEUE,
leading to silent failures.

Fixed this by returning -EOPNOTSUPP for tx_queue modifications and
ensuring proper error propagation in bnxt_re_configure_cc().

Fixes: 656dff55da19 ("RDMA/bnxt_re: Congestion control settings using debugfs hook")
Signed-off-by: Gautam R A <gautam-r.a@broadcom.com>
Link: https://patch.msgid.link/20250520035910.1061918-3-kalesh-anakkur.purayil@broadcom.com
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>