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

This reverts commit 1dd38766 which is
commit 3d07fa1d upstream.

It fixes a commit that is about to be reverted due to ABI breakage in
Android.  If needed, it can come back in in an abi-safe way in the
future.

Bug: 161946584
Change-Id: Ida127a7112c9748ffdccfd6c5498e2a8334ba3dc
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>