arm64: dts: qcom: sc7280: Mark SCM as dma-coherent for chrome devices

Just like for sc7180 devices using the Chrome bootflow (AKA trogdor
and IDP), sc7280 devices using the Chrome bootflow also need their
firmware marked dma-coherent. On sc7280 this wasn't causing WiFi to
fail to startup, since WiFi works differently there. However, on
sc7280 devices we were still getting the message at bootup after
commit 7bd6680 ("Revert "Revert "arm64: dma: Drop cache
invalidation from arch_dma_prep_coherent()"""):

 qcom_scm firmware:scm: Assign memory protection call failed -22
 qcom_rmtfs_mem 9c90000.memory: assign memory failed
 qcom_rmtfs_mem: probe of 9c90000.memory failed with error -22

We should mark SCM properly just like we did for trogdor.

Fixes: 7bd6680 ("Revert "Revert "arm64: dma: Drop cache invalidation from arch_dma_prep_coherent()""")
Fixes: 7a1f4e7 ("arm64: dts: qcom: sc7280: Add basic dts/dtsi files for sc7280 soc")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20230616081440.v2.4.I21dc14a63327bf81c6bb58fe8ed91dbdc9849ee2@changeid
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

Author: dianders

arch/arm64/boot/dts/qcom/sc7280-chrome-common.dtsi

@@ -79,6 +79,11 @@
 	firmware-name = "ath11k/WCN6750/hw1.0/wpss.mdt";
 };
 
+&scm {
+	/* TF-A firmware maps memory cached so mark dma-coherent to match. */
+	dma-coherent;
+};
+
 &wifi {
 	status = "okay";
 

arch/arm64/boot/dts/qcom/sc7280.dtsi

@@ -656,7 +656,7 @@
 	};
 
 	firmware {
-		scm {
+		scm: scm {
 			compatible = "qcom,scm-sc7280", "qcom,scm";
 		};
 	};