arm_adi_v5: Make the DAP API stateless

arm_adi_v5: Make the DAP API stateless

Remove entirely the concept of a "selected" AP that has to be maintained
between calls. All the information the DAP ops need are now provided to
each call through the AP/DAP pointer.

Consolidate the cache of the SELECT fields into one single field caching
the entire register.

Change-Id: I2e1c93ac5ee8ac38a7d680ca2c660c30093a6b87
Signed-off-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Reviewed-on: http://openocd.zylin.com/3165
Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>