remoteproc: qcom_q6v5_pas: Make single-PD handling more robust

Only go into the if condition for single-PD handling when there's
actually just one power domain specified there. Otherwise it'll be an
issue in the dts and we should fail in the regular code path.

This also mirrors the latest changes in the qcom_q6v5_mss driver.

Suggested-by: Stephan Gerhold <stephan.gerhold@linaro.org>
Fixes: 17ee2fb4 ("remoteproc: qcom: pas: Vote for active/proxy power domains")
Signed-off-by: Luca Weiss <luca@lucaweiss.eu>
Reviewed-by: Stephan Gerhold <stephan.gerhold@linaro.org>
Link: https://lore.kernel.org/r/20250128-pas-singlepd-v1-2-85d9ae4b0093@lucaweiss.eu


Signed-off-by: Bjorn Andersson <andersson@kernel.org>