x86/vmx: always sync PIR to IRR before vmentry

x86/vmx: always sync PIR to IRR before vmentry

When using posted interrupts on Intel hardware it's possible that the
vCPU resumes execution with a stale local APIC IRR register because
depending on the interrupts to be injected vlapic_has_pending_irq
might not be called, and thus PIR won't be synced into IRR.

Fix this by making sure PIR is always synced to IRR in
hvm_vcpu_has_pending_irq regardless of what interrupts are pending.

Reported-by: Joe Jin <joe.jin@oracle.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Tested-by: Joe Jin <joe.jin@oracle.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Juergen Gross <jgross@suse.com>