Revert "arm64: Stash shadow stack pointer in the task struct on interrupt"

This reverts commit 3f225f29 which is
commit 59b37fe5 upstream.

The shadow call stack for irq now is stored in current task's thread info
in irq_stack_entry. There is a possibility that we have some soft irqs
pending at the end of hard irq, and when we process softirq with the irq
enabled, irq_stack_entry will enter again and overwrite the shadow call
stack whitch stored in current task's thread info, leading to the
incorrect shadow call stack restoration for the first entry of the hard
IRQ, then the system end up with a panic.

task A                               |  task A
-------------------------------------+------------------------------------
el1_irq        //irq1 enter          |
  irq_handler  //save scs_sp1        |
    gic_handle_irq                   |
    irq_exit                         |
      __do_softirq                   |
                                     | el1_irq         //irq2 enter
                                     |   irq_handler   //save scs_sp2
                                     |                 //overwrite scs_sp1
                                     |   ...
                                     |   irq_stack_exit //restore scs_sp2
  irq_stack_exit //restore wrong     |
                 //scs_sp2           |

So revert this commit to fix it.

Fixes: 3f225f29

 ("arm64: Stash shadow stack pointer in the task struct on interrupt")
Signed-off-by: Xiang Yang <xiangyang3@huawei.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>