UPSTREAM: arm64: Add FIX_HOLE to permanent fixed addresses

Every other architecture with permanent fixed addresses has
FIX_HOLE as the first entry. This seems to be designed as a
debugging aid but there are a couple of side effects of not
having FIX_HOLE:

- If the first fixed address is 0, fix_to_virt -> virt_to_fix
triggers a BUG_ON for the virtual address being equal to
FIXADDR_TOP
- fix_to_virt may return a value outside of FIXADDR_START
and FIXADDR_TOP which may look like a bug to a developer.

Match up with other architectures and make everything clearer
by adding FIX_HOLE.

Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

(cherry picked from commit dab78b6dcb2bfc90038f35ada826844273dde4d6)
Signed-off-by: Tomasz Figa <tfiga@chromium.org>

Bug: 24475017

Change-Id: I495db3781f5b937c5e0cc47d53b18718335f78c6
Signed-off-by: Kees Cook <keescook@google.com>