common: Change custom request to 0x50

`0x30` is `USB_REQ_SET_SEL` which dwc3 will handle for us and it's going to complain and not send it.
`0x50` should be unused.

common/device.c

@@ -33,7 +33,7 @@ static const uint8_t heap_repair_data[] = {
 #define DEVICE_PRODUCT_ID 0x1234
 
 // custom request to upload data into the stack
-#define USB_REQ_CUSTOM 0x30
+#define USB_REQ_CUSTOM 0x50
 
 // location of the pEp0DmaBuf (containing the final rop, arm kernel and event)
 #define EP0DMABUF_LOCATION 0x1029d880u