dt-bindings: sram: sunxi: Populate valid sections compatibles

This adds a list of valid SRAM sections compatibles for the A13, A20,
A23 and H3 platforms. Per-platform compatibles are introduced for the
SRAM sections of these platforms, with the A10 compatibles also listed
as valid when applicable.

In particular, compatibles for the C1 SRAM section are introduced. Other
SRAMs (C2 and C3 in particular) are left out. They will be added we needed.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
[Maxime: Added the A10 compatible as fallback, not alternatives]
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>