kgdb,i386: Fix corner case access to ss with NMI watch dog exception
It is possible for the user_mode_vm(regs) check to return true on the
i368 arch for a non master kgdb cpu or when the master kgdb cpu
handles the NMI watch dog exception.
The solution is simply to select the correct gdb_ss location
based on the check to user_mode_vm(regs).
CC: Ingo Molnar <mingo@elte.hu> Acked-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Jason Wessel <jason.wessel@windriver.com>