arm64: dts: renesas: r8a77990: Add DRIF support

arm64: dts: renesas: r8a77990: Add DRIF support

Add the DRIF controller nodes for the r8a77990 (a.k.a. R-Car E3).

Please note that R-Car E3 has register BITCTR located at offset
0x80 (this register is not available on the r8a77960 and r8a77951,
whose support has already been upstreamed), and even though it is
not dealt with just yet within the driver, we have to keep that
into account with our device tree nodes.

Also, please note that while testing it has emerged that the
HW User Manual has the wrong DMA details for DRIF2 and DRIF3
on E3, as they are only allowed SYS-DMAC0 rather than SYS-DMAC1
and SYS-DMAC2. An errata addressing this issue will be available
soon.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Reviewed-by: Chris Paterson <chris.paterson2@renesas.com>
Link: https://lore.kernel.org/r/20200911121259.5669-1-fabrizio.castro.jz@renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>