sched/vtime: Move vtime accounting external declarations above inlines

Move the blob of external declarations (and their stubs) above the set of
inline definitions (and their stubs) for vtime accounting.  This will
allow a future patch to bring in more inline definitions without also
having to shuffle large chunks of code.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Link: https://lore.kernel.org/r/20210505002735.1684165-5-seanjc@google.com