net/mlx5e: Separate extended link modes request from link modes type selection

net/mlx5e: Separate extended link modes request from link modes type selection

The function ext_requested() serves two distinct purposes: it checks
if extended link modes were requested, and it selects whether to use
extended or legacy link modes.

This change separates these two purposes. Now, ext_link_mode_requested()
is used directly for checking if extended link modes are requested,
while the selection of extended modes is handled independently based on
the autonegotiation status.

By making this distinction, the logic for determining whether to select
extended or legacy link modes is clearer.

Signed-off-by: Shahar Shitrit <shshitrit@nvidia.com>
Reviewed-by: Carolina Jubran <cjubran@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20250219114112.403808-6-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>