arm64: dts: qcom: sdm845: Define guard pages within the rmtfs region

arm64: dts: qcom: sdm845: Define guard pages within the rmtfs region

Use qcom,use-guard-pages property instead of polluting device-tree with
lower and upper rmtfs guard nodes.

No functional change intended.

cosmetic: set name the node rmtfs-region.

Signed-off-by: David Heidelberg <david@ixit.cz>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Tested-By: Paul Sajna <sajattack@postmarketos.org>
Link: https://lore.kernel.org/r/20251020-sdm845-use-guard-pages-v1-1-64d714f8bd73@ixit.cz
Signed-off-by: Bjorn Andersson <andersson@kernel.org>