dt-bindings: interconnect: Add YAML schemas for QCOM bcm-voter

Add YAML schemas for interconnect bcm-voters found on QCOM RPMh-based
SoCs.

Signed-off-by: David Dai <daidavid1@codeaurora.org>
Signed-off-by: Odelu Kukatla <okukatla@codeaurora.org>
Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200209183411.17195-3-sibis@codeaurora.org
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>