[PATCH] KVM: add valid_vcpu() helper

Consolidate the logic for checking whether a vcpu index is valid.  Also, use
likely(), as a valid value should be the overwhelmingly common case.

Signed-off-by: James Morris <jmorris@namei.org>
Signed-off-by: Avi Kivity <avi@qumranet.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>