tools headers: Update the uapi/linux/perf_event.h copy with the kernel sources

To pick up the changes in:

c53e14f1ea4a8f8d perf: Extend per event callchain limit to branch stack

Addressing this perf tools build warning:

Warning: Kernel ABI header differences:
diff -u tools/include/uapi/linux/perf_event.h include/uapi/linux/perf_event.h

Please see tools/include/uapi/README for further details.

Acked-by: Ingo Molnar <[e-mail]>
Tested-by: Venkat Rao Bagalkote <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Namhyung Kim <[e-mail]>

tools/include/uapi/linux/perf_event.h

···
  *
  * @sample_max_stack: Max number of frame pointers in a callchain,
  *		      should be < /proc/sys/kernel/perf_event_max_stack
+ *		      Max number of entries of branch stack
+ *		      should be < hardware limit
  */
 struct perf_event_attr {