net: dsa: microchip: rename ksz9477_drive_strength_write()

ksz9477_drive_strength_write() isn't used for the KSZ9477-family only.
It's also used for the KSZ87xx chip variants. This function name is
misleading.

Rename it ksz_drive_strength_write().

Signed-off-by: Bastien Curutchet (Schneider Electric) <bastien.curutchet@bootlin.com>
Link: https://patch.msgid.link/20260702-clean-ksz-4th-v1-9-93441e695fa4@bootlin.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>