arm64: traps: simplify die() and __die()

In arm64's die and __die routines we pass around a thread_info, and
subsequently use this to determine the relevant task_struct, and the end
of the thread's stack. Subsequent patches will decouple thread_info from
the stack, and this approach will no longer work.

To figure out the end of the stack, we can use the new generic
end_of_stack() helper. As we only call __die() from die(), and die()
always deals with the current task, we can remove the parameter and have
both acquire current directly, which also makes it clear that __die
can't be called for arbitrary tasks.

Change-Id: Ia1a054760ac01a42207cdc933e6a0ada729ad1db
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Git-commit: 876e7a38e8788773aac768091aaa3b42e470c03b
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[ohaugan@codeaurora.org: Fix merge conflicts]
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>