ARM: dts: sun7i: Add support for the C1 SRAM region with the SRAM controller

This adds support for the C1 SRAM region (to be used with the SRAM
controller driver) for the A20 platform. The region is shared
between the Video Engine and the CPU.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
[Maxime: Fixed the SRAM C size]
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>