pinctrl: uniphier: add ethernet TX pin data for PXs3

PXs3 Ref boards need to change the strength of ethernet ports
for stability, like LD20's one.

This adds the table data and fixes the boot issue on PXs3 Ref board.

Fixes: 08520333 ("ARM: uniphier: sync with Linux 5.8-rc4")
Signed-off-by: Dai Okamura <okamura.dai@socionext.com>