cortex_a: Rename APB-AP to CPU in memory contexts

cortex_a: Rename APB-AP to CPU in memory contexts

Memory accesses are not made through the APB-AP, they are made through
the CPU (which happens to be controlled over the APB-AP). Rename all
irrelevant uses of the APB-AP term. And fix the long standing typo in
the function names...

Change-Id: Ide466fb2728930968bdba698f0dd9012cc9dbdf9
Signed-off-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Reviewed-on: http://openocd.zylin.com/3216
Tested-by: jenkins
Reviewed-by: Andreas Färber <afaerber@suse.de>
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>