Use defined VID/PIDs instead of magic numbers

src/stlink-common.h

@@ -23,6 +23,7 @@ extern "C" {
     // st-link vendor cmd's
 #define USB_ST_VID			0x0483
 #define USB_STLINK_PID			0x3744
+#define USB_STLINK_32L_PID		0x3748
 
     // STLINK_DEBUG_RESETSYS, etc:
 #define STLINK_OK			0x80

src/stlink-usb.c

@@ -136,10 +136,10 @@ static int is_stlink_device(libusb_device * dev) {
 
     printf("device: 0x%04x, 0x%04x\n", desc.idVendor, desc.idProduct);
 
-    if (desc.idVendor != 0x0483)
+    if (desc.idVendor != USB_ST_VID)
         return 0;
 
-    if (desc.idProduct != 0x3748)
+    if (desc.idProduct != USB_STLINK_32L_PID)
         return 0;
 
     return 1;