In 4.14.57, a new symbol for Spectre v4 mitigation was introduced for
ARM64. Add this symbol to all ARM64 targets using kernel 4.14.
This mitigates CVE-2018-3639 on ARM64.
Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>
(cherry picked from commit 77e3e706ce)