Annotate guest printf helpers with __printf() so that the compiler will
warn about incorrect formatting at compile time (see git log for how easy
it is to screw up with the formatting).
Suggested-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20231129224916.532431-5-seanjc@google.comSigned-off-by: Sean Christopherson <seanjc@google.com>