UPSTREAM: arm64: Fix reference to docs for ARM64_TAGGED_ADDR_ABI

(Upstream commit 799c85105233514309b201a2d2d7a7934458c999).

The referenced file does not exist, but tagged-address-abi.rst does.

Signed-off-by: Jeremy Cline <jcline@redhat.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Bug: 135692346
Change-Id: Id87593870acd680e37254db234da3536be1b0028