net: phy: aquantia: remove handling for get_rate_matching(PHY_INTERFACE_MODE_NA)

net: phy: aquantia: remove handling for get_rate_matching(PHY_INTERFACE_MODE_NA)

After commit 7642cc28fd37 ("net: phylink: fix PHY validation with rate
adaption"), the API contract changed and PHY drivers are no longer
required to respond to the .get_rate_matching() method for
PHY_INTERFACE_MODE_NA. This was later followed up by documentation
commit 6d4cfcf97986 ("net: phy: Update documentation for
get_rate_matching").

As such, handling PHY_INTERFACE_MODE_NA in the Aquantia PHY driver
implementation of this method is unnecessary and confusing. Remove it.

Cc: Sean Anderson <sean.anderson@seco.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20250821152022.1065237-8-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>