adi_v5: search for Debug and Memory AP support

Adds dap_find_ap() function.

Change-Id: I6643025624009b12d4936de67a605da52c07be49
Signed-off-by: Evan Hunter <ehunter@broadcom.com>
Reviewed-on: http://openocd.zylin.com/909
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>