dt-bindings: sram: qcom,imem: document SM6375 IMEM

Add a compatible for SM6375 IMEM.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230303-topic-sm6375_features0_dts-v2-3-708b8191f7eb@linaro.org