For wearables target, compilation happens along with PDK.
Due to compilation with PDK, tree structure changes to compile kernel
modules.
$BOARD_COMMON_DIR allows to use top-level-makefile specified value,
else it defaults to device/qcom/common for other targets.
Change-Id: I8a32f655175933cc2abe95779284097f3bcb53cc
Signed-off-by: Kaustubh Pandey <quic_kapandey@quicinc.com>