Coding standard patch of M290

Marlin/Marlin_main.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 = parser.value_axis_units(a);
-          offs = constrain(offs, -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 = parser.value_axis_units(Z_AXIS);
-        offs = constrain(offs, -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