MXSCM-236 mx6dqscm: adjust some ddr calibration parameters

Some adjustment to the ddr configuration like:

- Precharge all commands per JEDEC
- Fix the space partition values for 2Gb
- Fix other values that reduce yield of scm parts
  per testing perfomed

Signed-off-by: Juan Gutierrez <juan.gutierrez@nxp.com>