realtek: pcs: replace __free() auto-cleanup stuff

realtek: pcs: replace __free() auto-cleanup stuff

Upstream netdev maintainers disregard both variable declarations
mid-function and usage of __free() for auto-cleanup [1]. To avoid any
pain when trying to upstream the PCS driver at some point, adjust that
now before forgetting it.

[1] https://www.kernel.org/doc/html/next/process/maintainer-netdev.html#using-device-managed-and-cleanup-h-constructs

Link: https://github.com/openwrt/openwrt/pull/23694
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>