powerpc/kexec: Fix return of uninitialized variable

of_property_read_u64() can fail and leave the variable uninitialized,
which will then be used. Return error if reading the property failed.

Fixes: 2e6bd221d96f ("powerpc/kexec_file: Enable early kernel OPAL calls")
Signed-off-by: Zhang Zekun <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

arch/powerpc/kexec/file_load_64.c

···
 	if (dn) {
 		u64 val;
 
-		of_property_read_u64(dn, "opal-base-address", &val);
+		ret = of_property_read_u64(dn, "opal-base-address", &val);
+		if (ret)
+			goto out;
+
 		ret = kexec_purgatory_get_set_symbol(image, "opal_base", &val,
 						     sizeof(val), false);
 		if (ret)
 			goto out;
 
-		of_property_read_u64(dn, "opal-entry-address", &val);
+		ret = of_property_read_u64(dn, "opal-entry-address", &val);
+		if (ret)
+			goto out;
 		ret = kexec_purgatory_get_set_symbol(image, "opal_entry", &val,
 						     sizeof(val), false);
 	}