perf tools: Import rb_erase_init from block/ in the kernel sources

I was assuming rb_erase() was setting things up like list_del_init, but
the fact that thread__delete() was being sucessfull is because the last
thing before deleting is to remove the thread from the
machine->dead_threads list, using list_del_init(), that has the same
effect as using rb_erase_init()...

Introduce this function so that we can use it when removing objects from
rb_trees.

Then we will be able to BUG_ON(still on a list) in destructors.

Cc: Adrian Hunter <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Don Zickus <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Stephane Eranian <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

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