IMPORTANT cpu frequency vs temperature fixes

While compiling a large app I noticed the temperature rising without CPU frequency changing, hence dug in the dvfs code and found it was broken.

Here is a couple of commits that fix that so CPU frequency throttles a bit when temperature rises, just enough so as to make MUCH more unlikely to hit dangerous temperatures with high work loads.

Minor changes:
- Added 126 MHz frequency for an even lower power consumption while idle
- olegk0's fixes to yaffs2 fs without smp_lock