net: stmmac: dwmac-qcom-ethqos: rename a label in probe()

The err_mem label's name is unclear. It actually should be reached on
any error after stmmac_probe_config_dt() succeeds. Name it after the
cleanup action that needs to be called before exiting.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Andrew Halaney <ahalaney@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>