drivers/vdebug: add support for DAP level interface

This patch adds support for DAP interface to Cadence vdebug driver.
It implements a new transport layer for dapdirect_swd.

Change-Id: I64b02a9e1ce91e552e07fca692879655496f88b6
Signed-off-by: Jacek Wuwer <jacekmw8@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/6965
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

tcl/board/vd_a53x2_dap.cfg

@@ -0,0 +1,29 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+# Cadence virtual debug interface
+# Arm Cortex A53x2 through DAP
+
+source [find interface/vdebug.cfg]
+
+set _CORES 2
+set _CHIPNAME a53
+set _MEMSTART 0x00000000
+set _MEMSIZE 0x1000000
+
+# vdebug select transport
+transport select dapdirect_swd
+
+# JTAG reset config, frequency and reset delay
+adapter speed 50000
+adapter srst delay 5
+
+# BFM hierarchical path and input clk period
+vdebug bfm_path tbench.u_vd_swdp_bfm 10ns
+
+# DMA Memories to access backdoor (up to 4)
+vdebug mem_path tbench.u_memory.mem_array $_MEMSTART $_MEMSIZE
+
+source [find target/swj-dp.tcl]
+
+swj_newdap $_CHIPNAME cpu -irlen 4 -ircapture 0x1 -irmask 0xf
+
+source [find target/vd_aarch64.cfg]