wiphone isn't setting a valid backlight enable pin

Therefore don't just randomly be writing to a GPIO numbered -1
Instead just don't try to control the backlight
NOTE: I don't have a 'wiphone' to test with, but I saw this via inspection
while cleaning up some other stuff.

variants/wiphone/variant.h

@@ -34,13 +34,17 @@
 #define ST7789_SCK 18
 #define ST7789_CS 5
 #define ST7789_RS 26
-#define ST7789_BL -1 // EXTENDER_PIN(9)
+// I don't have a 'wiphone' but this I think should not be defined this way (don't set TFT_BL if we don't have a hw way to control
+// it)
+// #define ST7789_BL -1 // EXTENDER_PIN(9)
 
 #define ST7789_RESET -1
 #define ST7789_MISO 19
 #define ST7789_BUSY -1
 #define ST7789_SPI_HOST SPI3_HOST
-#define TFT_BL -1 // EXTENDER_PIN(9)
+// I don't have a 'wiphone' but this I think should not be defined this way (don't set TFT_BL if we don't have a hw way to control
+// it)
+// #define TFT_BL -1 // EXTENDER_PIN(9)
 #define SPI_FREQUENCY 40000000
 #define SPI_READ_FREQUENCY 16000000
 #define TFT_HEIGHT 240