rp2040: don't compile in host code when in device mode

src/portable/raspberrypi/rp2040/rp2040_usb.h

@@ -71,11 +71,13 @@ struct hw_endpoint
     uint len;
     // Amount of data with the hardware
     uint transfer_size;
+#ifdef RP2040_USB_HOST_MODE
     // Only needed for host mode
     bool last_buf;
     // HOST BUG. Host will incorrect write status to top half of buffer
     // control register when doing transfers > 1 packet
     uint8_t buf_sel;
+#endif
     // User buffer in main memory
     uint8_t *user_buf;
 
@@ -84,11 +86,13 @@ struct hw_endpoint
     // Interrupt, bulk, etc
     uint8_t transfer_type;
     
+#ifdef RP2040_USB_HOST_MODE
     // Only needed for host
     uint8_t dev_addr;
     bool sent_setup;
     // If interrupt endpoint
     uint8_t interrupt_num;
+#endif
 };
 
 void rp2040_usb_init(void);