interconnect: qcom: constify qcom_icc_bcm pointers

Pointers to struct qcom_icc_bcm are not modified, so they can be made
const for safety.  The contents of struct qcom_icc_bcm must stay
non-const.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220412102623.227607-3-krzysztof.kozlowski@linaro.org
Signed-off-by: Georgi Djakov <djakov@kernel.org>