net: dsa: tag_rtl8_4: fix typo in modalias name

DSA_TAG_PROTO_RTL8_4L is not defined. It should be
DSA_TAG_PROTO_RTL8_4T.

Fixes: cd87fecd

 ("net: dsa: tag_rtl8_4: add rtl8_4t trailing variant")
Reported-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20220309175641.12943-1-luizluca@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>