Note about MKS_MINI_12864 in sanitycheck

Marlin/src/inc/SanityCheck.h

  *       SAV_3DGLCD => U8GLIB_SH1106 => ULTIMAKERCONTROLLER
  *       MKS_12864OLED => U8GLIB_SH1106 => ULTIMAKERCONTROLLER
  *       MKS_12864OLED_SSD1306 => U8GLIB_SSD1306 => ULTIMAKERCONTROLLER
+ *       MKS_MINI_12864 => MINIPANEL
  *       miniVIKI => ULTIMAKERCONTROLLER
  *       VIKI2 => ULTIMAKERCONTROLLER
  *       ELB_FULL_GRAPHIC_CONTROLLER => ULTIMAKERCONTROLLER