Permit D6 (MISO) to be used for DC to save on pins

Using D6 (MISO) for the DC line is not recommended as transaction support and TFT reads may cause it to become and input!
However if a hardware setup has no other pins spare, then this is an option that can be tried.

TFT_eSPI.cpp

@@ -151,6 +151,10 @@ void TFT_eSPI::init(void)
 
   // SPI1U1 |= SPIUSIO; // Single I/O pin on MOSI (bi-directional) - not tested
  
+  // Set to output once again incase D6 (MISO) is used for DC
+  digitalWrite(TFT_DC, HIGH); // Data/Command high = data mode
+  pinMode(TFT_DC, OUTPUT);
+
   // toggle RST low to reset
 #ifdef TFT_RST
   if (TFT_RST >= 0) {