Disable splash-screen when done once

Splash screen was shown with every display init.
That means every time the menus where entered.

Note the 2 in the initialisation.
The buffer is already written in two steps a 512 byte.
Without the 2 only the upper half is shown.

Marlin/dogm_lcd_implementation.h

@@ -186,6 +186,8 @@ char lcd_printPGM(const char* str) {
   return n;
 }
 
+static int8_t show_splashscreed = 2;
+
 static void lcd_implementation_init()
 {
   #ifdef LCD_PIN_BL // Enable LCD backlight
@@ -219,6 +221,7 @@ static void lcd_implementation_init()
 
 	u8g.firstPage();
 	do {
+    if (show_splashscreed) {
       u8g.drawBitmapP(offx, offy, START_BMPBYTEWIDTH, START_BMPHEIGHT, start_bmp);
       lcd_setFont(FONT_MENU);
       #ifndef STRING_SPLASH_LINE2
@@ -228,6 +231,8 @@ static void lcd_implementation_init()
         u8g.drawStr(txt1X, u8g.getHeight() - DOG_CHAR_HEIGHT*3/2, STRING_SPLASH_LINE1);
         u8g.drawStr(txt2X, u8g.getHeight() - DOG_CHAR_HEIGHT*1/2, STRING_SPLASH_LINE2);
       #endif
+      show_splashscreed--;
+    }
 	} while (u8g.nextPage());
 }