Revert "tracing: Zero the pipe cpumask on alloc to avoid spurious -EBUSY"

This reverts commit 99a8d14d which is
commit 3d07fa1d upstream.

The commit it fixes is about to be reverted, so also revert it.

Bug: 161946584
Change-Id: I0c442ffd94cfe75b8d61318d2913de9b818ba7f3
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>