net: pylink.h: add kernel-doc descriptions for new fields at phylink_config

Some fields were moved from struct phylink into phylink_config.
Update the kernel-doc markups for the config struct accordingly

Fixes: 5c05c1db ("net: phylink, dsa: eliminate phylink_fixed_state_cb()")
Reviewed-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/34970f447ff86415a6cef10a785fbef81c2819a7.1592895969.git.mchehab+huawei@kernel.org


Signed-off-by: Jonathan Corbet <corbet@lwn.net>