added dcd_sof_enable(), tud_sof_isr_set()

make number of interface configurable (default to 8)
CFG_TUD_INTERFACE_MAX

src/device/usbd.h

@@ -33,6 +33,8 @@
 extern "C" {
 #endif
 
+typedef void (*tud_sof_isr_t) (uint32_t frame_count);
+
 //--------------------------------------------------------------------+
 // Application API
 //--------------------------------------------------------------------+
@@ -84,6 +86,10 @@ bool tud_disconnect(void);
 // Return false on unsupported MCUs
 bool tud_connect(void);
 
+// Set Start-of-frame (1ms interval) IRQ handler
+// NULL means disabled, frame_count may not be supported on mcus
+void tud_sof_isr_set(tud_sof_isr_t sof_isr);
+
 // Carry out Data and Status stage of control transfer
 // - If len = 0, it is equivalent to sending status only
 // - If len > wLength : it will be truncated