net: ethtool: mm: sanitize some UAPI configurations

The verify-enabled boolean (ETHTOOL_A_MM_VERIFY_ENABLED) was intended to
be a sub-setting of tx-enabled (ETHTOOL_A_MM_TX_ENABLED). IOW, MAC Merge
TX can be enabled with or without verification, but verification with TX
disabled makes no sense.

The pmac-enabled boolean (ETHTOOL_A_MM_PMAC_ENABLED) was intended to be
a global toggle from an API perspective, whereas tx-enabled just handles
the TX direction. IOW, the pMAC can be enabled with or without TX, but
it doesn't make sense to enable TX if the pMAC is not enabled.

Add two checks which sanitize and reject these invalid cases.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>