package/xen: bump version to 4.14.2

Includes a number of bugfixes and the security fixes up to 368, so drop
those.

For details, see the release notes:
https://xenproject.org/downloads/xen-project-archives/xen-project-4-14-series/xen-project-4-14-2/



Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>