We should send uevent to userspace whenever the link speed or width
changes but tb_switch_asym_enable() and tb_switch_asym_disable() set the
sw->link_width already so tb_switch_update_link_attributes() never
noticed the change.

Fix this so that we let tb_switch_update_link_attributes() update the
fields accordingly.

Fixes: 81af2952 ("thunderbolt: Add support for asymmetric link")
Reported-by: Pengfei Xu <pengfei.xu@intel.com>
Tested-by: Pengfei Xu <pengfei.xu@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>