MN10300: Make the kernel jump into gdbstub on a BUG

Make the kernel jump into gdbstub (if configured) on a BUG with the register
set from the BUG rather than interpolating another illegal instruction and
leaving gdbstub's idea of the process counter in unsupported_syscall() where
the original BUG was detected.

With this patch, gdbstub reports a SIGABRT to the compiler and reports the
program counter at the original BUG, allowing the execution state at the time
of the BUG to be examined with GDB.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/mn10300/kernel/traps.c

@@ -391,7 +391,7 @@ static asmlinkage void unsupported_syscall(struct pt_regs *regs,
 	if (code == EXCEP_SYSCALL15 && !user_mode(regs)) {
 		if (report_bug(regs->pc, regs) == BUG_TRAP_TYPE_BUG) {
 #ifdef CONFIG_GDBSTUB
-			__gdbstub_bug_trap();
+			gdbstub_intercept(regs, code);
 #endif
 		}
 	}