arm: dts: k3-*-binman: Make default DM file optional

The default DM firmware path is non-optional as of now. Make it
optional so that users that choose to provide DM via TI_DM argument
instead of BINMAN_INDIRS can do so without build errors.

Signed-off-by: Neha Malcom Francis <n-francis@ti.com>
Reviewed-by: Kamlesh Gurudasani <kamlesh@ti.com>
diff --git a/arch/arm/dts/k3-am62p-sk-binman.dtsi b/arch/arm/dts/k3-am62p-sk-binman.dtsi
index dea1494..2233921 100644
--- a/arch/arm/dts/k3-am62p-sk-binman.dtsi
+++ b/arch/arm/dts/k3-am62p-sk-binman.dtsi
@@ -72,6 +72,7 @@
 
 		blob-ext {
 			filename = "ti-dm/am62pxx/ipc_echo_testb_mcu1_0_release_strip.xer5f";
+			optional;
 		};
 	};