VMX: constrain vmx_intr_assist() debugging code to debug builds

VMX: constrain vmx_intr_assist() debugging code to debug builds

This is because that code, added by commit 997382b771 ("y86/vmx: dump
PIR and vIRR before ASSERT()"), was meant to be removed by the time we
finalize 4.9, but the root cause of the ASSERT() wrongly(?) triggering
still wasn't found.

Take the opportunity and also correct the format specifiers, which I
had got wrong when editing said change while committing.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>
Release-Acked-by: Julien Grall <julien.grall@arm.com>