Mostly reusing DDR3 driver, this patch adds DDR4 SPD handling, register
calculation and programming.
Signed-off-by: NYork Sun <yorksun@freescale.com>

The numeric constants in the switch statements are replaced by #defines
added to the common ddr_spd.h header.  This dramatically improves the
readability of the switch statments.

In addition, a few of the longer lines were cleaned up, and the DDR2
type for an SO-RDIMM module was added to the DDR2 switch statement.
Signed-off-by: NKyle Moffett <Kyle.D.Moffett@boeing.com>
Cc: Andy Fleming <afleming@gmail.com>
Cc: Kim Phillips <kim.phillips@freescale.com>
Acked-by: NYork Sun <yorksun@freescale.com>
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>

SPD has minor change from Rev 1.2 to 1.3. This patch enables Rev 1.3.
The difference has ben examined and the code is compatible.
Speed bins is not verified on hardware for CL7 at this moment.

This patch also enables SPD Rev 1.x where x is up to "F". According to SPD
spec, the lower nibble is optionally used to determine which additinal bytes
or attribute bits have been defined. Software can safely use defaults. However,
the upper nibble should always be checked.
Signed-off-by: NYork Sun <yorksun@freescale.com>
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>

- support mirrored DIMMs, not support register DIMMs
- test passed on P2020DS board with MT9JSF12872AY-1G1D1
- test passed on MPC8569MDS board with MT8JSF12864HY-1G1D1
Signed-off-by: NDave Liu <daveliu@freescale.com>
Signed-off-by: NTravis Wheatley <travis.wheatley@freescale.com>

Also adds helper functions for DDR1/2 to verify the checksum.
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>