arm64: defconfig: Enable CONFIG_PHY_RCAR_GEN3_PCIE

Enable R-Car Gen3 PCIe PHY support, which is needed for PCIe to function
on the Renesas Condor board.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>