ARM: dts: sun8i: R40: Add SPI controllers nodes and pinmuxes

The Allwinner R40 SoC contains four SPI controllers, using the newer
sun6i design (but at the legacy addresses).
The controller seems to be fully compatible to the A64 one, so no driver
changes are necessary.
The first three controllers can be used on two sets of pins, but SPI3 is
only routed to one set on Port A.
Only the pin groups for SPI0 on PortC and SPI1 on PortI are added here,
because those seem to be the only one exposed on the Bananapi boards.

Tested by connecting a SPI flash to a Bananapi M2 Berry SPI0 and SPI1
header pins.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>