remoteproc: qcom_q6v5_mss: Use a carveout to authenticate modem headers

Any access to the dynamically allocated metadata region by the application
processor after assigning it to the remote Q6 will result in a XPU
violation. Fix this by replacing the dynamically allocated memory region
with a no-map carveout and unmap the modem metadata memory region before
passing control to the remote Q6.

Reported-and-tested-by: Amit Pundir <amit.pundir@linaro.org>
Fixes: 6c5a9dc2

 ("remoteproc: qcom: Make secure world call for mem ownership switch")
Signed-off-by: Sibi Sankar <quic_sibis@quicinc.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230117085840.32356-7-quic_sibis@quicinc.com