fix(morello): dts: fix SCMI shmem/mboxes grouping

The official Arm MHU DT binding suggests to group the shmem (and mboxes)
values to signify the number of mailboxes supported.
Linux' "make dtbs_check" reports:
============
.../morello-soc.dt.yaml: scmi: shmem:0: [17, 18] is too long
        From schema: dt-schema.git/dtschema/schemas/mbox/mbox-consumer.yaml
============

Add angle brackets at the right location to mark the boundaries between
the two mailbox instances used.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Change-Id: If585c98b5e8e55cd5c0b1261e03ce4b91a4c0413

fdts/morello-fvp.dts

@@ -144,8 +144,8 @@
 		scmi {
 			compatible = "arm,scmi";
 			mbox-names = "tx", "rx";
-			mboxes = <&mailbox 1 0 &mailbox 1 1>;
-			shmem = <&cpu_scp_hpri0 &cpu_scp_hpri1>;
+			mboxes = <&mailbox 1 0>, <&mailbox 1 1>;
+			shmem = <&cpu_scp_hpri0>, <&cpu_scp_hpri1>;
 			#address-cells = <1>;
 			#size-cells = <0>;
 

fdts/morello-soc.dts

@@ -221,8 +221,8 @@
 		scmi {
 			compatible = "arm,scmi";
 			mbox-names = "tx", "rx";
-			mboxes = <&mailbox 1 0 &mailbox 1 1>;
-			shmem = <&cpu_scp_hpri0 &cpu_scp_hpri1>;
+			mboxes = <&mailbox 1 0>, <&mailbox 1 1>;
+			shmem = <&cpu_scp_hpri0>, <&cpu_scp_hpri1>;
 			#address-cells = <1>;
 			#size-cells = <0>;
 			scmi_dvfs: protocol@13 {