net: stmmac: dwmac-qcom-ethqos: use a helper variable for &pdev->dev

Shrink code and avoid line breaks by using a helper variable for
&pdev->dev.

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