rtems-fdt: hold handle ref until end of rtems_fdt_prop_value

Fixes #5608

cpukit/libmisc/rtems-fdt/rtems-fdt.c

@@ -893,12 +893,13 @@ int rtems_fdt_prop_value(
   }
 
   prop = rtems_fdt_getprop( &fdt, node, propname, &length );
-  rtems_fdt_release_handle( &fdt );
   if ( length < 0 ) {
+    rtems_fdt_release_handle( &fdt );
     return length;
   }
 
   if ( length > (int) *size ) {
+    rtems_fdt_release_handle( &fdt );
     return -RTEMS_FDT_ERR_BADPATH;
   }
 
@@ -906,6 +907,7 @@ int rtems_fdt_prop_value(
 
   memcpy( value, prop, length );
 
+  rtems_fdt_release_handle( &fdt );
   return 0;
 }