hv: refine pass-thru device specific vmsix function

- write_vmsix_cap_reg(): emulates vmsix cap writes.
   write_pt_vmsix_cap_reg(): emulates msix cap write
   for PT devices.

 - rw_vmsix_table(): emulates vmsix table bar space access.

 - vmsix_handle_table_mmio_access(): emulates the vmsix
   bar space access only.

 - pt_vmsix_handle_table_mmio_access(): emulates the vmsix
   bar space access and remap msi entry for PT device if
   write operation is executed.

 - rename 'init_vmsix()' and 'deinit_vmsix()' to
   'init_vmsix_pt()' and 'deinit_vmsix_pt()' respectively,
   they're for PT devices only.

  - remove below 2 functions,call
        'pci_vdev_read_vcfg()' directly in cases they're used.
        - 'read_vmsi_cap_reg()'
        - 'read_vmsix_cap_reg()'

Tracked-On: #5407
Signed-off-by: Yonghua Huang <yonghua.huang@intel.com>
Reviewed-by: Li, Fei <fei1.li@intel.com>
Reviewed-by: Wang, Yu1 <yu1.wang@intel.com>
Acked-by: Eddie Done <eddie.dong@intel.com>

hypervisor/dm/vpci/vmsi.c

@@ -95,15 +95,6 @@ static void remap_vmsi(const struct pci_vdev *vdev)
 	}
 }
 
-/**
- * @pre vdev != NULL
- */
-void read_vmsi_cap_reg(const struct pci_vdev *vdev, uint32_t offset, uint32_t bytes, uint32_t *val)
-{
-	/* For PIO access, we emulate Capability Structures only */
-	*val = pci_vdev_read_vcfg(vdev, offset, bytes);
-}
-
 /**
  * @brief Writing MSI Capability Structure
  *