UAPI: x86: Move pvclock-abi to UAPI for x86 platforms

UAPI: x86: Move pvclock-abi to UAPI for x86 platforms

KVM provides a new interface for performing a fixup/correction of the KVM
clock against the reference TSC. The KVM_[GS]ET_CLOCK_GUEST API requires a
pvclock_vcpu_time_info, as such the caller must know about this definition.

Move the definition to the UAPI folder so that it is exported to usermode
and also change the type definitions to use the standard for UAPI exports.

Signed-off-by: Jack Allister <jalliste@amazon.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>