linux-ramdump-parser-v2: Cleanup task dumping

Several of the fields of the task are not being read out as
'true size'. Use more appropriate functions. At the same time,
factor out the reading of pc/fc/sp into a ramdump specific
functionality since that code may be architectur specific.

Change-Id: I5d7bd14031a4431aa665207e8e31e3ecb7dd1cdb