net/mlx5e: Don't override user RSS upon set channels

[ Upstream commit 5a8e1267 ]

Currently, increasing the number of combined channels is changing
the RSS spread to use the new created channels.
Prevent the RSS spread change in case the user explicitly declare it,
to avoid overriding user configuration.

Tested:
when RSS default:

# ethtool -L ens8 combined 4
RSS spread will change and point to 4 channels.

# ethtool -X ens8 equal 4
# ethtool -L ens8 combined 6
RSS will not change after increasing the number of the channels.

Fixes: 8bf36862 ('ethtool: ensure channel counts are within bounds during SCHANNELS')
Signed-off-by: Inbar Karmy <inbark@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>