tracing: Fix irqs-off tag display in syscall tracing

commit 11034ae9c20f4057a6127fc965906417978e69b2 upstream

Initialization of variable irq_flags and pc was missed when backport
11034ae9c to linux-3.0.y and linux-3.4.y, my fault.

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: PipelinerArd <kristoferard@gmail.com>