tracing: Remove unused TRACE_SEQ_BUF_USED

This macro isn't used from commit 3a161d99 ("tracing: Create
seq_buf layer in trace_seq"). so no needs to keep it.

Link: http://lkml.kernel.org/r/1579586086-45543-1-git-send-email-alex.shi@linux.alibaba.comSigned-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace_seq.c

@@ -30,9 +30,6 @@
 /* How much buffer is left on the trace_seq? */
 #define TRACE_SEQ_BUF_LEFT(s) seq_buf_buffer_left(&(s)->seq)
 
-/* How much buffer is written? */
-#define TRACE_SEQ_BUF_USED(s) seq_buf_used(&(s)->seq)
-
 /*
  * trace_seq should work with being initialized with 0s.
  */