arm64: dts: renesas: r8a774a1: Enable DMA for SCIF2

SCIF2 on RZ/G2M can be used with both DMAC1 and DMAC2.

Fixes: 3a3933a4 ("arm64: dts: renesas: r8a774a1: Add SCIF and HSCIF nodes")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>