ARM: dts: qcom: fix node name for rpm-msg-ram

Adjust the name to match the bindings and fix the following validation
error:

<snip>/arch/arm/boot/dts/qcom-apq8026-huawei-sturgeon.dtb: memory@fc428000: $nodename:0: 'memory@fc428000' does not match '^sram(@.*)?'
        From schema: <snip>/Documentation/devicetree/bindings/sram/sram.yaml

Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220924145126.24978-1-luca@z3ntu.xyz