stlink: expose ap number and csw in memory r/w

stlink: expose ap number and csw in memory r/w

Recent versions of stlink firmware allow accessing access port
other than zero and setting the CSW.

Modify the internal API to provide ap_num and csw.
There is no interest to modify HLA to use ap_num and csw, so set
and use some backward compatible defaults.

Change-Id: I3f6dfc6c670d19467d9f5e717c6c956db6faf7f3
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/6602
Tested-by: jenkins
Reviewed-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>