Revert "bpf: Do not include stack ptr register in precision backtracking bookkeeping"

This reverts commit 4265682c which is
commit e2d2115e upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I1a833012ae4ccf639e468eedc82f6c1b93db87bc
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>