Update u8g / AVR display timing defaults (#21518)

Marlin/src/lcd/dogm/ultralcd_st7920_u8glib_rrd_AVR.cpp

 #include "ultralcd_st7920_u8glib_rrd_AVR.h"
 
 #if F_CPU >= 20000000
-  #define CPU_ST7920_DELAY_1 DELAY_NS(0)
+  #define CPU_ST7920_DELAY_1 DELAY_NS(150)
   #define CPU_ST7920_DELAY_2 DELAY_NS(0)
-  #define CPU_ST7920_DELAY_3 DELAY_NS(50)
+  #define CPU_ST7920_DELAY_3 DELAY_NS(150)
 #elif MB(3DRAG, K8200, K8400)
   #define CPU_ST7920_DELAY_1 DELAY_NS(0)
   #define CPU_ST7920_DELAY_2 DELAY_NS(188)
   #define CPU_ST7920_DELAY_2 DELAY_NS(40)
   #define CPU_ST7920_DELAY_3 DELAY_NS(340)
 #elif F_CPU == 16000000
-  #define CPU_ST7920_DELAY_1 DELAY_NS(0)
+  #define CPU_ST7920_DELAY_1 DELAY_NS(125)
   #define CPU_ST7920_DELAY_2 DELAY_NS(0)
-  #define CPU_ST7920_DELAY_3 DELAY_NS(63)
+  #define CPU_ST7920_DELAY_3 DELAY_NS(125)
 #else
   #error "No valid condition for delays in 'ultralcd_st7920_u8glib_rrd_AVR.h'"
 #endif