arm_adi_v5: Do not ignore register polling timeout

arm_adi_v5: Do not ignore register polling timeout

Previous to this commit 'ahbap_debugport_init' would ignore if timeout
happened or not when waiting for CDBGPWRUPACK and CSYSPWRUPACK and would
continue initialization regardless. It also would not reset the
timeout counter after finishing polling for CDBGPWRUPACK and starting
for CSYSPWRUPACK which could potentially cause some problems.

Also refactor code of both snippets into a more generic function to
avoid duplication.

Change-Id: I16e4f50e6819e08c4126e71ef8cec7db559d608e
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Reviewed-on: http://openocd.zylin.com/2086
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Tested-by: jenkins