dt-bindings: interconnect: qcom-bwmon: document SM8550 compatibles

Document the compatibles used to describe the Bandwidth Monitors
present on the SM8550 platform.

A BWMON v4 IP monitors the CPU bandwidth, and a v5 does the LLCC
bandwidth monitoring.

This is described by adding "llcc" and "cpu" into the compatible
strings to differentiate the BWMON IPs.

Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>