arm: dts: k3-j721s2|am68: Migrate to OF_UPSTREAM

Use OF_UPSTREAM to pull Linux DT from dts/ tree

Signed-off-by: Manorit Chawdhry <m-chawdhry@ti.com>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index c9f1b25..60660f2 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -1331,9 +1331,7 @@
 			      k3-j721e-beagleboneai64.dtb \
 			      k3-j721e-r5-beagleboneai64.dtb
 
-dtb-$(CONFIG_SOC_K3_J721S2) += k3-am68-sk-base-board.dtb\
-			       k3-am68-sk-r5-base-board.dtb\
-			       k3-j721s2-common-proc-board.dtb\
+dtb-$(CONFIG_SOC_K3_J721S2) += k3-am68-sk-r5-base-board.dtb\
 			       k3-j721s2-r5-common-proc-board.dtb
 
 dtb-$(CONFIG_SOC_K3_J784S4) += k3-am69-r5-sk.dtb \