Enabled registered DIMMs using data from SPD. RDIMMs have registers
which need to be configured before using. The register configuration
words are stored in SPD byte 60~116 (JEDEC standard No.21-C). Software
should read those RCWs and put into DDR controller before initialization.

Signed-off-by: York Sun <yorksun@freescale.com>

- 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: Dave Liu <daveliu@freescale.com>
Signed-off-by: Travis Wheatley <travis.wheatley@freescale.com>

Also adds helper functions for DDR1/2 to verify the checksum.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>