ARM: dts: qcom: sdx65: add dedicated IMEM and syscon compatibles

Add proper compatibles to the IMEM device node:
1. syscon as required by the bindings, even though it is not currently
   used,
2. dedicated compatible as required for syscon and simple-mfd nodes.

Align the node name to match IMEM type of device - SRAM.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221104190840.134733-2-krzysztof.kozlowski@linaro.org