dt-bindings: mtd: partitions: Add binding for Qcom SMEM parser

Add YAML binding for Qualcomm Shared Memory (SMEM) Flash partition
parser.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210104041137.113075-2-manivannan.sadhasivam@linaro.org