net: ethernet: mtk_eth_soc: Always call mtk_gmac0_rgmii_adjust() for mt7623

Modify mtk_gmac0_rgmii_adjust() so it can always be called.
mtk_gmac0_rgmii_adjust() sets-up the TRGMII clocks.

Signed-off-by: René van Dorst <opensource@vdorst.com>
Signed-off-By: David Woodhouse <dwmw2@infradead.org>
Tested-by: Frank Wunderlich <frank-w@public-files.de>
Signed-off-by: David S. Miller <davem@davemloft.net>