arm64: defconfig: Enable RPC-IF support

Enable moduler support for the Renesas SPI Multi I/O Bus Controller
(RPC-IF), which is used on the Condor, Eagle, V3HSK, and V3MSK boards.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200819101240.12260-1-geert+renesas@glider.be