mem: Add support for more flexible DRAM timing and topologies

mem: Add support for more flexible DRAM timing and topologies

This patch has 2 main aspects:
1) Add new parameter to adjust write-to-write delay
2) Enable support of more than 64 banks per controller

Changes for new parameter:
Incorporated a new parameter, tCCD_L_WR, which defaults to tCCD_L.
This parameter can be used to set a unique delay between writes and
between reads.

To incorporate this parameter in the controller, modified the DRAMCtrl
class to have separate variables for read and write column delays.
Used these variables to account for tRTW, tWTR, tBURST, tCCD_L, and tCS
as well as the new tCCD_L_WR parameter.

Changes to support more than 64 banks:
Modified the logic selecting the next command (reorderQueue
and minBankPrep functions).  Replaced the unint64_t variables with
a vector of uint32_t elements.  There is a uint32_t element defined
per ranks to allow up to 32 banks per rank.  This will automatically
scale with ranks without issue.
Change will allow analysis of memory sub-systems beyond the current
landscape.

Change-Id: I0ce466efed58276f843ad90e9ecc0ece6c37d646
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/10103
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>