net: Temporarily backout SKB sources tracer.

net: Temporarily backout SKB sources tracer.

Steven Rostedt has suggested that Neil work with the tracing
folks, trying to use TRACE_EVENT as the mechanism for
implementation.  And if that doesn't workout we can investigate
other solutions such as that one which was tried here.

This reverts the following 2 commits:

a9fd0c62771c9a6de440aabc0921dd3e2d2a0c02
("net: skb ftracer - Add config option to enable new ftracer (v3)")

bd7d22af4487adcc9f2f569402dc004d61193922
("net: skb ftracer - Add actual ftrace code to kernel (v3)")

Signed-off-by: David S. Miller <davem@davemloft.net>