fix(draw): fix sw compile error when disable LV_DRAW_SW_COMPLEX (#6895)

Signed-off-by: lhdjply <lhdjply@126.com>

src/draw/sw/lv_draw_sw_mask_private.h

@@ -16,6 +16,8 @@ extern "C" {
 
 #include "lv_draw_sw_mask.h"
 
+#if LV_DRAW_SW_COMPLEX
+
 /*********************
  *      DEFINES
  *********************/
@@ -146,6 +148,8 @@ void lv_draw_sw_mask_cleanup(void);
  *      MACROS
  **********************/
 
+#endif  /*LV_DRAW_SW_COMPLEX*/
+
 #ifdef __cplusplus
 } /*extern "C"*/
 #endif