soc: qcom: rmtfs: Support discarding guard pages

soc: qcom: rmtfs: Support discarding guard pages

In some configurations, the exact placement of the rmtfs shared memory
region isn't so strict. The DeviceTree author can then choose to use the
"size" property and rely on the OS for placement (in combination with
"alloc-ranges", if desired).

But on some platforms the rmtfs memory region may not be allocated
adjacent to regions allocated by other clients. Add support for
discarding the first and last 4k block in the region, if
qcom,use-guard-pages is specified in DeviceTree.

Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Reviewed-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20230920-rmtfs-mem-guard-pages-v3-2-305b37219b78@quicinc.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>