kprobes/x86: Call BUG() when reentering probe into KPROBES_HIT_SS

Call BUG() when a probe have been hit on the way of kprobe processing
path, because that kind of probes are currently unrecoverable
(recovering it will cause an infinite loop and stack overflow).

The original code seems to assume that it's caused by an int3
which another subsystem inserted on out-of-line singlestep buffer if
the hitting probe is same as current probe. However, in that case,
int3-hitting-address is on the out-of-line buffer and should be
different from first (current) int3 address.
Thus, I decided to remove the code.

I also removes arch_disarm_kprobe() because it will involve other stuffs
in text_poke().

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
LKML-Reference: <20090827172258.8246.61889.stgit@localhost.localdomain>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>