Fix Kinetis bug causing USB to get stuck sending

If an IN endpoint is stalled during a transfer by writing to the
USB ENDPOINT register then the data being sent will repeat and flood
the USB bus. This patch prevents the register write from occurring by
instead writing to the buffer descriptor in RAM and letting the USB
hardware handle setting the stall bit.

Note - Control requests on endpoint 0 do still set the STALL bit
directly. This is not a problem since control endpoints cannot be
stalled externally while a transfer is ongoing.

Author: c1728p9

usb/device/targets/TARGET_Freescale/USBPhy_Kinetis.cpp

@@ -411,11 +411,23 @@ void USBPhyHw::endpoint_remove(usb_ep_t endpoint)
 
 void USBPhyHw::endpoint_stall(usb_ep_t endpoint)
 {
-    USB0->ENDPOINT[DESC_TO_LOG(endpoint)].ENDPT |= USB_ENDPT_EPSTALL_MASK;
+    if (DESC_TO_LOG(endpoint) == 0) {
+        USB0->ENDPOINT[DESC_TO_LOG(endpoint)].ENDPT |= USB_ENDPT_EPSTALL_MASK;
+    } else {
+        uint8_t dir = DESC_EP_IN(endpoint) ? TX : RX;
+        uint32_t idx = EP_BDT_IDX(DESC_TO_LOG(endpoint), dir, 0);
+        bdt[idx].info |= BD_OWN_MASK | BD_STALL_MASK;
+    }
 }
 
 void USBPhyHw::endpoint_unstall(usb_ep_t endpoint)
 {
+
+    if (DESC_TO_LOG(endpoint) != 0) {
+        uint8_t dir = DESC_EP_IN(endpoint) ? TX : RX;
+        uint32_t idx = EP_BDT_IDX(DESC_TO_LOG(endpoint), dir, 0);
+        bdt[idx].info &= ~(BD_OWN_MASK | BD_STALL_MASK);
+    }
     USB0->ENDPOINT[DESC_TO_LOG(endpoint)].ENDPT &= ~USB_ENDPT_EPSTALL_MASK;
 }