ANDROID: GKI: soc: qcom: export `irq_stack_ptr`

The Qualcomm minidump feature needs irq_stack_ptr for debugging with
ramdumps. Export it.

Bug: 172988823
Bug: 176525217
Change-Id: I3e3de735f017a17b912ae10e1153ae5fd27636ef
Signed-off-by: Lucas Wei <lucaswei@google.com>
Signed-off-by: Will McVicker <willmcvicker@google.com>