Fix CoreXY homing bug introduced by PR #1606

The Check Endstop logic must be:

if (current_block->steps_x != current_block->steps_y || (TEST(out_bits,
X_AXIS) == TEST(out_bits, Y_AXIS)))
if (TEST(out_bits, X_HEAD))

not

if (TEST(out_bits, X_HEAD) && (current_block->steps_x !=
current_block->steps_y || (TEST(out_bits, X_AXIS) == TEST(out_bits,
Y_AXIS))))

Same applies for Y axis.

Marlin/stepper.cpp

@@ -413,7 +413,8 @@ ISR(TIMER1_COMPA_vect) {
       #else
         // Head direction in -X axis for CoreXY bots.
         // If DeltaX == -DeltaY, the movement is only in Y axis
-        if (TEST(out_bits, X_HEAD) && (current_block->steps_x != current_block->steps_y || (TEST(out_bits, X_AXIS) == TEST(out_bits, Y_AXIS))))
+        if (current_block->steps_x != current_block->steps_y || (TEST(out_bits, X_AXIS) == TEST(out_bits, Y_AXIS)))      
+            if (TEST(out_bits, X_HEAD))
       #endif
             { // -direction
               #ifdef DUAL_X_CARRIAGE
@@ -437,13 +438,13 @@ ISR(TIMER1_COMPA_vect) {
                   #endif
                 }
             }
-
       #ifndef COREXY
         if (TEST(out_bits, Y_AXIS))   // -direction
       #else
         // Head direction in -Y axis for CoreXY bots.
         // If DeltaX == DeltaY, the movement is only in X axis
-          if (TEST(out_bits, Y_HEAD) && (current_block->steps_x != current_block->steps_y || (TEST(out_bits, X_AXIS) != TEST(out_bits, Y_AXIS))))
+        if (current_block->steps_x != current_block->steps_y || (TEST(out_bits, X_AXIS) != TEST(out_bits, Y_AXIS)))
+            if (TEST(out_bits, Y_HEAD))             
       #endif
             { // -direction
               #if defined(Y_MIN_PIN) && Y_MIN_PIN >= 0