[esp32] Define BUTTON_PIN (-1) by default, fixes #6213 (#6371)

Signed-off-by: Andrew Yong <me@ndoo.sg>

src/configuration.h

@@ -110,6 +110,11 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 // Define if screen should be mirrored left to right
 // #define SCREEN_MIRROR
 
+// Define BUTTON_PIN to ensure button setup is always done
+#ifndef BUTTON_PIN
+#define BUTTON_PIN (-1)
+#endif
+
 // I2C Keyboards (M5Stack, RAK14004, T-Deck)
 #define CARDKB_ADDR 0x5F
 #define TDECK_KB_ADDR 0x55