net: dsa: microchip: Add register access control for KSZ8873 chip

This update introduces specific register access boundaries for the
KSZ8873 and KSZ8863 chips within the DSA Microchip driver. The outlined
ranges target global control registers, port registers, and advanced
control registers.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>