net: phy: realtek: get rid of magic numbers in rtl8201_config_intr()

net: phy: realtek: get rid of magic numbers in rtl8201_config_intr()

Replace the magic numbers with defines. Register names were obtained from
publicly available documentation[1]. This should make it clear what's going
on in the code.

1. RTL8201F/RTL8201FL/RTL8201FN Rev. 1.4 Datasheet
Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
Reviewed-by: Daniel Golle <daniel@makrotopia.org>
Reviewed-by: Nicolai Buchwitz nb@tipi-net.de
Link: https://patch.msgid.link/20260406201222.1043396-1-olek2@wp.pl
Signed-off-by: Jakub Kicinski <kuba@kernel.org>