arm64: dts: qcom: Fix node name of rpm-msg-ram device nodes

According to the new DT schema for qcom,rpm-msg-ram the node name
should be sram@. memory@ is reserved for definition of physical RAM
(usable by Linux).

This fixes the following dtbs_check error on various device trees:
memory@60000: 'device_type' is a required property
        From schema: dtschema/schemas/memory.yaml

Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211018110009.30837-1-stephan@gerhold.net