arm64: dts: qcom: msm8916/39: Move mpss_mem size to boards

The modem firmware size is typically highly device-specific.
The current size of the mpss_mem region in msm8916.dtsi (0x2b00000)
only works for some APQ8016 devices without full-featured modem,
such as the DragonBoard 410c.

The full modem firmware is typically about twice as large (~45 MiB
-> ~90 MiB) but also varies by a few MiB from device to device. Since
these devices are quite memory-constrained nowadays it's important to
minimize the unnecessary memory reservations.

Make it clear that each board needs to specify the necessary mpss_mem
size by replacing the DB410c-specific size in msm8916.dtsi with a
simple comment. &mpss_mem is disabled by default so it's fine to leave
some properties up to the boards if they want to enable it.

Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20230911-msm8916-rmem-v1-8-b7089ec3e3a1@gerhold.net
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

arch/arm64/boot/dts/qcom/apq8016-sbc.dts

@@ -263,6 +263,7 @@ &mpss {
 
 &mpss_mem {
 	status = "okay";
+	reg = <0x0 0x86800000 0x0 0x2b00000>;
 };
 
 &pm8916_codec {

arch/arm64/boot/dts/qcom/msm8916.dtsi

@@ -84,7 +84,7 @@ mpss_mem: mpss@86800000 {
 			 * alignment = <0x0 0x400000>;
 			 * alloc-ranges = <0x0 0x86800000 0x0 0x8000000>;
 			 */
-			reg = <0x0 0x86800000 0x0 0x2b00000>;
+			reg = <0x0 0x86800000 0x0 0>; /* size is device-specific */
 			no-map;
 			status = "disabled";
 		};

arch/arm64/boot/dts/qcom/msm8939.dtsi

@@ -356,7 +356,7 @@ mpss_mem: mpss@86800000 {
 			 * alignment = <0x0 0x400000>;
 			 * alloc-ranges = <0x0 0x86800000 0x0 0x8000000>;
 			 */
-			reg = <0x0 0x86800000 0x0 0x5500000>;
+			reg = <0x0 0x86800000 0x0 0>; /* size is device-specific */
 			no-map;
 			status = "disabled";
 		};