arch/tile: support signal "exception-trace" hook

This change adds support for /proc/sys/debug/exception-trace to tile.
Like x86 and sparc, by default it is set to "1", generating a one-line
printk whenever a user process crashes.  By setting it to "2", we get
a much more complete userspace diagnostic at crash time, including
a user-space backtrace, register dump, and memory dump around the
address of the crash.

Some vestiges of the Tilera-internal version of this support are
removed with this patch (the show_crashinfo variable and the
arch_coredump_signal function).  We retain a "crashinfo" boot parameter
which allows you to set the boot-time value of exception-trace.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
diff --git a/arch/tile/include/asm/signal.h b/arch/tile/include/asm/signal.h
index 81d92a4..1e1e616 100644
--- a/arch/tile/include/asm/signal.h
+++ b/arch/tile/include/asm/signal.h
@@ -28,6 +28,10 @@
 int restore_sigcontext(struct pt_regs *, struct sigcontext __user *);
 int setup_sigcontext(struct sigcontext __user *, struct pt_regs *);
 void do_signal(struct pt_regs *regs);
+void signal_fault(const char *type, struct pt_regs *,
+		  void __user *frame, int sig);
+void trace_unhandled_signal(const char *type, struct pt_regs *regs,
+			    unsigned long address, int signo);
 #endif
 
 #endif /* _ASM_TILE_SIGNAL_H */