kprobes: remove called_from argument

Remove called_from argument from kprobes which had been used for
preventing self-refering of kernel module.  However, since we don't keep
module's refcount after registering kprobe any more, there is no reason to
check that.

This patch also simplifies registering/unregistering functions because we
don't need to use __builtin_return_address(0) which was passed to
called_from.

[ananth@in.ibm.com: build fix]
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>