net: dsa: Fix typo in NET_DSA_TAG_RTL4_A Kconfig

Fix a minor typo in the help text for the NET_DSA_TAG_RTL4_A config
option.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Link: https://lore.kernel.org/r/20240607020843.1380735-1-chris.packham@alliedtelesis.co.nz


Signed-off-by: Jakub Kicinski <kuba@kernel.org>