Coding standard patch of M290

Marlin/src/gcode/motion/M290.cpp

   #if ENABLED(BABYSTEP_XY)
     for (uint8_t a = X_AXIS; a <= Z_AXIS; a++)
       if (parser.seenval(axis_codes[a]) || (a == Z_AXIS && parser.seenval('S'))) {
-        float offs = constrain(parser.value_axis_units(a), -2, 2);
+        const float offs = constrain(parser.value_axis_units(a), -2, 2);
         #if ENABLED(BABYSTEP_ZPROBE_OFFSET)
           if (a == Z_AXIS) {
             zprobe_zoffset += offs;
       }
   #else
     if (parser.seenval('Z') || parser.seenval('S')) {
-      float offs = constrain(parser.value_axis_units(Z_AXIS), -2, 2);
+      const float offs = constrain(parser.value_axis_units(Z_AXIS), -2, 2);
       #if ENABLED(BABYSTEP_ZPROBE_OFFSET)
         zprobe_zoffset += offs;
         refresh_zprobe_zoffset(); // This will babystep the axis