mv88e6xxx: Refactor 6352's serdes functions

mv88e6xxx: Refactor 6352's serdes functions

Changes:
1. Replace serdes check by mv88e6352_g2_scratch_port_has_serdes in
mv88e6352_pcs_init function by mv88e6xxx_serdes_get_lane function making it
more generic.
2. Replace serdes checks in mv88e6352_serdes_get_* functions with
mv88e6xxx_serdes_get_lane making them more generic.
3. Add lane argument to mv88e6352_serdes_read so it can be reused later for
6321.

Co-developed-by: Thomas Eckerman <thomas.eckerman.ext@ericsson.com>
Signed-off-by: Thomas Eckerman <thomas.eckerman.ext@ericsson.com>
Signed-off-by: Fidan Aliyeva <fidan.aliyeva.ext@ericsson.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20260528210310.1365858-3-fidan.aliyeva.ext@ericsson.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>