arm64: factor out current_stack_pointer

We define current_stack_pointer in <asm/thread_info.h>, though other
files and header relying upon it do not have this necessary include, and
are thus fragile to changes in the header soup.

Subsequent patches will affect the header soup such that directly
including <asm/thread_info.h> may result in a circular header include in
some of these cases, so we can't simply include <asm/thread_info.h>.

Instead, factor current_thread_info into its own header, and have all
existing users include this explicitly.

Change-Id: If434675e803479f53e6b72e2ca1cf71c420d6d2f
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: a9ea0017ebe8889dfa136cac2aa7ae0ee6915e1f
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>