Checks for CR10_STOCKDISPLAY with Creality v4 (#19019)

Marlin/src/pins/stm32f1/pins_CREALITY_V4.h

 #define ONBOARD_SD_CS_PIN                   PA4   // SDSS
 #define SDIO_SUPPORT
 
+#if ENABLED(CR10_STOCKDISPLAY) && NONE(RET6_12864_LCD, VET6_12864_LCD)
+  #error "Define RET6_12864_LCD or VET6_12864_LCD to select pins for CR10_STOCKDISPLAY with the Creality V4 controller."
+#endif
+
 #if ENABLED(RET6_12864_LCD)
 
   /* RET6 12864 LCD */
   #define BTN_EN2                           PB14
 
   #define BEEPER_PIN                        PC6
+
 #elif ENABLED(VET6_12864_LCD)
 
   /* VET6 12864 LCD */