adiv6: prepare for AP level ROM tables

adiv6: prepare for AP level ROM tables

ADIv6 adds AP that only contain a ROM table in the AP itself, that
can point to other AP containing either another AP level ROM table
or a MEM-AP to be parsed as usual.

To handle recursive AP access, reorganize the code to:
- pass the depth==0 from the command 'dap info';
- print the AP number as first line, adding proper indentation on
  depth>0;
- align the following print with proper indentation.

Change-Id: I5b811810c807fc51b307bd60f67817d9de2aa095
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/6466
Tested-by: jenkins