net/mlx5: Bridge, correct config option description

The implication of the previous help text was that without this option
enabled, representor devices couldn't be added to a bridge device, while
in fact that was possible, just that rules didn't get offloaded to hw.

This commit clarifies the help text.

Signed-off-by: Cosmin Ratiu <cratiu@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20250219114112.403808-2-tariqt@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>