dt-bindings: mfd: Document smp-memram subnode for aspeed,ast2x00-scu

dt-bindings: mfd: Document smp-memram subnode for aspeed,ast2x00-scu

The platform initialisation code for the AST2600 implements the custom
SMP bringup protocol, and searches for the relevant compatible. As a
consequence, define the requisite node and the compatible string, which
in-turn tidies up the dtb check results.

Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20260109-dev-dt-warnings-mfd-v1-1-1aabe37e9a14@codeconstruct.com.au
Signed-off-by: Lee Jones <lee@kernel.org>