Blackfin: add C define of trace_buffer_init()

Have the C API trace funcs match the assembly API trace funcs.
Signed-off-by: Graf Yang <graf.yang@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

arch/blackfin/include/asm/trace.h

@@ -28,6 +28,8 @@ extern unsigned long software_trace_buff[];
 
 #ifdef CONFIG_DEBUG_BFIN_HWTRACE_ON
 
+#define trace_buffer_init() bfin_write_TBUFCTL(BFIN_TRACE_INIT)
+
 #define trace_buffer_save(x) \
 	do { \
 		(x) = bfin_read_TBUFCTL(); \