fgpa: Change output pins to pull high by default.

Pull output pins high when their output isn't enabled. They are pulled
high because SPI CS and UART TX lines should default to being pulled
high.

rtl/fpga/top_sonata.sv

@@ -422,8 +422,10 @@ module top_sonata
   assign in_from_pins[IN_PIN_SER0_RX     ] = ser0_rx;
 
   // Output Pins
-  // pull output pins low when their output isn't enabled.
-  assign output_pins = out_to_pins_en & out_to_pins;
+  // Pull output pins high when their output isn't enabled.
+  // They are pulled high because SPI CS and UART TX lines
+  // should default to being pulled high.
+  assign output_pins = out_to_pins | ~out_to_pins_en;
 
   assign microsd_dat3 = output_pins[OUT_PIN_MICROSD_DAT3];
   assign microsd_cmd  = output_pins[OUT_PIN_MICROSD_CMD ];