Build - [HAX] Allow per-target dtbTool

Original_Change-Id: I97ecb0448ae7bd5859454be290c5dde6248b2859

build: Default to dtbToolCM

* The default dtbTool isn't the correct module name for the module that
actually lives in device/qcom/common/dtbtool

Change-Id: I80b427e3652b99742573bc4d2829e51645a8822b
Signed-off-by: STELIX <ssspinni@gmail.com>