vfio/pci-quirks: Make vfio_add_*_cap() return bool

This is to follow the coding standand in qapi/error.h to return bool
for bool-valued functions.

Include below functions:
vfio_add_virt_caps()
vfio_add_nv_gpudirect_cap()
vfio_add_vmd_shadow_cap()

Suggested-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
3 files changed