Add missing power-domain "mxc" required by CDSP PAS remoteproc on SM8350
SoC.

Fixes: e8b4e9a2 ("remoteproc: qcom: pas: Add SM8350 PAS remoteprocs")
Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
Cc: stable@vger.kernel.org
Tested-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/1624559605-29847-1-git-send-email-sibis@codeaurora.org