Merge pull request #4119 from thinkyhead/fix_stepper_compile_error

Fix stepper compile error with motor_current_setting

.travis.yml

   - opt_enable BQ_LCD_SMART_CONTROLLER SPEAKER
   - build_marlin
   #
+  # Test MINIRAMBO for PWM_MOTOR_CURRENT
+  #
+  - restore_configs
+  - opt_set MOTHERBOARD BOARD_MINIRAMBO
+  - build_marlin
+  #
   # Enable FILAMENTCHANGEENABLE
   #
   - restore_configs

Marlin/stepper.h

       #ifndef PWM_MOTOR_CURRENT
         #define PWM_MOTOR_CURRENT DEFAULT_PWM_MOTOR_CURRENT
       #endif
-      const int motor_current_setting[3] = PWM_MOTOR_CURRENT;
+      static constexpr int motor_current_setting[3] = PWM_MOTOR_CURRENT;
     #endif
 
     //