arm: tegra: emc: add emc training timer

arm: tegra: emc: add emc training timer

Add an EMC training timer by making the dram_therm code more generic.
The old dram_therm code maintained a single timer. This patch reuses
some of that old code and cleans up some other code as well. Many of
the debugfs nodes were simplifed. Other functions and bits of data
were renamed.

Change-Id: I5cf7f11d2684c8d5d422fc64bf47ae38e194f63e
Signed-off-by: Alex Waterman <alexw@nvidia.com>
Reviewed-on: http://git-master/r/660450
(cherry picked from commit dfa173e6ce60d4c2c54a57c26cb0553b0043325d)
Reviewed-on: http://git-master/r/663394
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Mitch Luban <mluban@nvidia.com>