32-bit variant of the previous patch for 64-bit:

<<
    When an interrupt occurs in userspace, we can call trace_hardirqs_on/off()
    With one level stack. But if we have irqsoff tracing enabled,
    it checks both CALLER_ADDR0 and CALLER_ADDR1. The second call
    goes two stack frames up. If this is from user space, then there may
    not exist a second stack....
>>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>