arm_adi_v5: separate ROM table parsing from command output [1/3]

arm_adi_v5: separate ROM table parsing from command output [1/3]

In OpenOCD arm_adi_v5 we have already two implementations of code
for parsing the ADIv5 ROM table:
- in the commands "dap info" and "$dap_name info";
- in the function dap_lookup_cs_component().
Adding support for ADIv6 requires extending both implementations.

Moreover, current code does not handle few aspects of the ROM
parsing, e.g. the "Power Domain IDs".
To add such extensions both implementations should be touched.

I plan to add a command to parses (again) the ROM table and dump a
simple prototype of a configuration script for the target, useful
while analysing a new target.

Keeping aligned all these implementation would be too complex.

With focus to "dap info" command, decouple the part of code to
walk-through the ROM table from the code that creates the command
output.
The idea is to keep a single implementation for the walk-through
code, while parametrizing the output code to handle the generation
of a configuration script or the result of the function
dap_lookup_cs_component().

This change only targets the output of MEM-AP header
Further changes will target other parts of the code.

While there, add a message if MEM-AP is not accessible.

Change-Id: I112f637edfdb8688afb4e631297f6536da9604f1
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/6819
Tested-by: jenkins