mlxsw: cmd: Edit the comment of 'max_lag' field in CONFIG_PROFILE

Starting from Spectrum-4, the maximum number of LAG IDs can be configured
by software via CONFIG_PROFILE command during driver initialization.

Edit the comment of 'max_lag' field to mention that this field is reserved
in Spectrum-1/2/3 and describe firmware behavior.

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>