Allows dumping out current register contents from the debug filesystem, and
also allows user to add arbitrary register save points into code. Current
register contents are available under debugfs at:

[debugfs]/pm_debug/registers/current

To add a save point, do following:

From module init (or somewhere before the save call, called only once):
  pm_dbg_init_regset(n); // n=1..4, allocates memory for dump area #n

From arbitrary code location:
  pm_dbg_regset_save(n); // n=1..4, saves registers to dump area #n

After this, the register dump can be seen under [debugfs]/pm_debug/registers/n
Signed-off-by: NTero Kristo <tero.kristo@nokia.com>
Signed-off-by: NKevin Hilman <khilman@deeprootsystems.com>