memory: emif: handle frequency and voltage change events

Change SDRAM timings and other settings as necessary
on voltage and frequency changes. We calculate these
register settings based on data from the device data
sheet and inputs such a frequency, voltage state(stable
or ramping), temperature level etc.

TODO: frequency and voltage change handling needs to
be integrated with clock framework and regulator
framework respectively. This is not done today
due to missing pieces in the kernel.

Signed-off-by: Aneesh V <[email protected]>
Reviewed-by: Santosh Shilimkar <[email protected]>
Reviewed-by: Benoit Cousson <[email protected]>
[[email protected]: Moved to drivers/memory from drivers/misc]
Signed-off-by: Santosh Shilimkar <[email protected]>
Tested-by: Lokesh Vutla <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>