kprobes/x86: Move ftrace-based kprobe code into kprobes-ftrace.c

kprobes/x86: Move ftrace-based kprobe code into kprobes-ftrace.c

Split ftrace-based kprobes code from kprobes, and introduce
CONFIG_(HAVE_)KPROBES_ON_FTRACE Kconfig flags.
For the cleanup reason, this also moves kprobe_ftrace check
into skip_singlestep.

Link: http://lkml.kernel.org/r/[email protected]
Cc: Ingo Molnar <[email protected]>
Cc: Ananth N Mavinakayanahalli <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Signed-off-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>