Fill in posted interrupt fields (vector, pda, etc) and set mode to 1 to
enable VT-d PI (posted mode) for this ptdev.
If intr_src->pi_vcpu is 0, fall back to use the remapped mode.
Tracked-On: #4506
Signed-off-by: dongshen <dongsheng.x.zhang@intel.com>
Reviewed-by: Eddie Dong <eddie.dong@Intel.com>