net: phylink: allow half-duplex modes with RATE_MATCH_PAUSE

PHYs performing rate-matching using MAC-side flow-control always
perform duplex-matching as well in case they are supporting
half-duplex modes at all.
No longer remove half-duplex modes from their capabilities.

Suggested-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/b157c0c289cfba024039a96e635d037f9d946745.1728617993.git.daniel@makrotopia.org


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