fix LCD build for devboard

src/nrf52/UC1701Spi.cpp

@@ -36,15 +36,18 @@ class UC1701Spi : public OLEDDisplay
 };
 
 #include "variant.h"
+
+#ifdef ERC12864_CS
 #include <UC1701.h>
 static UC1701 lcd(PIN_SPI_SCK, PIN_SPI_MOSI, ERC12864_CS, ERC12864_CD);
 
+void testLCD()
+{
+    // PCD8544-compatible displays may have a different resolution...
+    lcd.begin();
 
-void testLCD() {
-  // PCD8544-compatible displays may have a different resolution...
-  lcd.begin();
-
-  // Write a piece of text on the first line...
-  lcd.setCursor(0, 0);
-  lcd.print("Hello, World!");
-}
+    // Write a piece of text on the first line...
+    lcd.setCursor(0, 0);
+    lcd.print("Hello, World!");
+}
+#endif