Blackfin arch: give sys_strace proper entry markings

a global _sys_trace will cause the assembler to fail, it should be fixed in toolchain side firstly.
Signed-off-by: NMike Frysinger <vapier.adi@gmail.com>
Signed-off-by: NBryan Wu <cooloney@kernel.org>

arch/blackfin/mach-common/entry.S

@@ -704,6 +704,9 @@ ENTRY(_system_call)
 	rts;
 ENDPROC(_system_call)
 
+/* Do not mark as ENTRY() to avoid error in assembler ...
+ * this symbol need not be global anyways, so ...
+ */
 _sys_trace:
 	call _syscall_trace;