Re-enable DDR simulation in the COMA code.
Re-enable DDR simulation in the COMA code.

The cleanup code from July 16th
(14ac77f2e38130fbda3356a30621d4cf9897f746) had surreptitiously
disabled us of the DDR channel timing simulation, thereby
"accelerating" the COMA code unrealistically. This patch re-activates
the DDR channel in the simulaiton path.

Bitblade-org/mgsim,Bitblade-org/mgsim,Bitblade-org/mgsim,Bitblade-org/mgsim