arm64: dts: qcom: sc7180: Mark SCM as dma-coherent for IDP

sc7180-idp is, for most intents and purposes, a trogdor device.
Specifically, sc7180-idp is designed to run the same style of firmware
as trogdor devices. This can be seen from the fact that IDP has the
same "Reserved memory changes" in its device tree that trogdor has.

Recently it was realized that we need to mark SCM as dma-coherent to
match what trogdor's style of firmware (based on TF-A) does [1]. That
means we need this dma-coherent tag on IDP as well.

Without this, on newer versions of Linux, specifically those with
commit 7bd6680 ("Revert "Revert "arm64: dma: Drop cache
invalidation from arch_dma_prep_coherent()"""), WiFi will fail to
work. At bootup you'll see:

  qcom_scm firmware:scm: Assign memory protection call failed -22
  qcom_rmtfs_mem 94600000.memory: assign memory failed
  qcom_rmtfs_mem: probe of 94600000.memory failed with error -22

[1] https://lore.kernel.org/r/20230615145253.1.Ic62daa649b47b656b313551d646c4de9a7da4bd4@changeid

Fixes: 7bd6680 ("Revert "Revert "arm64: dma: Drop cache invalidation from arch_dma_prep_coherent()""")
Fixes: f5ab220 ("arm64: dts: qcom: sc7180: Add remoteproc enablers")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20230616081440.v2.2.I3c17d546d553378aa8a0c68c3fe04bccea7cba17@changeid
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

Author: dianders

arch/arm64/boot/dts/qcom/sc7180-idp.dts

@@ -393,6 +393,11 @@
 	qcom,spare-regs = <&tcsr_regs_2 0xb3e4>;
 };
 
+&scm {
+	/* TF-A firmware maps memory cached so mark dma-coherent to match. */
+	dma-coherent;
+};
+
 &sdhc_1 {
 	status = "okay";
 

arch/arm64/boot/dts/qcom/sc7180.dtsi

@@ -369,7 +369,7 @@
 	};
 
 	firmware {
-		scm {
+		scm: scm {
 			compatible = "qcom,scm-sc7180", "qcom,scm";
 		};
 	};