Move kernel and modules based on CONFIG_ZONE_DMA=y

Move kernel and modules based on CONFIG_ZONE_DMA=y instead of
CONFIG_COMCERTO_ZONE_DMA_NCNB=y.

This change allows CONFIG_COMCERTO_ZONE_DMA_NCNB to be disabled
without affecting physical memory layout.

Whether CONFIG_ZONE_DMA is enabled alone or together with
CONFIG_COMCERTO_ZONE_DMA_NCNB, we want the memory layout to be:
 0MB-44MB: DMA zone
44MB-64MB: COMCERTO_DDR_SHARED_BASE
64MB-    : Linux kernel

Optimus uses:
CONFIG_ZONE_DMA=y
CONFIG_COMCERTO_ZONE_DMA_NCNB=y

SpaceCast uses:
CONFIG_ZONE_DMA=y
CONFIG_COMCERTO_ZONE_DMA_NCNB=n

This change complements the changes:
commit 24fc119798ca8da0b50a950b594358550510f5fb
Author: Matthias Kaehlcke <mka@google.com>
Date:   Mon Oct 5 12:12:17 2015 -0700
Comcerto: Enable ZONE_DMA

commit 289dfb638cbc3257483093a16447ffc99ce01281
Author: Matthias Kaehlcke <mka@google.com>
Date:   Mon Oct 5 12:25:48 2015 -0700
Comcerto: Only change text offset when DMA NCNB is enabled

Change-Id: I688f57bfc01bd445f102e92d73100f3a634901ca
3 files changed