kprobes: Prohibit to probe native_get_debugreg

Since do_debug() calls get_debugreg(), native_get_debugreg() will be
called from singlestepping. This can cause an int3 infinite loop.

We can't put it in the .text.kprobes section because it is inlined,
then we blacklist its name.

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: <20090827172332.8246.34194.stgit@localhost.localdomain>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>