On some platform the remote processor's memory map is not statically
configured in TrustZone, so each memory region that is to be accessed by
the remote needs a call into TrustZone to set up the remote's
permissions.

Implement this for the rmtfs memory driver, to give the modem on 8996
access to the shared file system buffers.
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>