Change in coreboot[master]: nb/intel/x4x/raminit: Rework receive enable calibration

[Arthur Heymans (Code Review)]

Hello Paul Menzel, build bot (Jenkins), coreboot org, Nico Huber,

I'd like you to reexamine a change.  Please visit

https://review.coreboot.org/18692

to look at the new patch set (#23).

Change subject: nb/intel/x4x/raminit: Rework receive enable calibration
......................................................................

nb/intel/x4x/raminit: Rework receive enable calibration

Moves receive enable calibration to a separate file to lighten
raminit.c a bit.

Receive enable calibration is quite similar to gm45 so it reuses some
of its function names.

The functional changes are:
* the minimum coarse is now reset for each channel;
* on the second fine search for DQS high, TAP overflow is handled by
  increasing medium;
* start coarse at CAS + 1 instead of CAS - 1. Other Intel northbridges
  do the same and the results are more in line with register dumps
  from vendor bios.
These might improve stability.

TESTED on ga-g41m-es2l

Change-Id: I0c970455e609d3ce96a262cbf110336a2079da4d
Signed-off-by: Arthur Heymans 
---
M src/northbridge/intel/x4x/Makefile.inc
M src/northbridge/intel/x4x/raminit_ddr2.c
A src/northbridge/intel/x4x/rcven.c
M src/northbridge/intel/x4x/x4x.h
4 files changed, 368 insertions(+), 282 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/92/18692/23