libtracefs: Update documentation for tracefs_hist_alloc_nd_cnt()

As tracefs_hist_alloc_nd_cnt() was added too, add it to the documentation
man pages, and also update the main libtracefs man page to include both:

  tracefs_hist_add_key_cnt()
  tracefs_hist_alloc_nd_cnt()

Link: https://lore.kernel.org/linux-trace-devel/20221021163853.6f5ffb2c@gandalf.local.home

Fixes: faa0ba7f ("libtracefs: Add buckets field to tracefs_sql() function")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2 files changed