wandboard: Set fdt based on board_rev and board_name

wandboard: Set fdt based on board_rev and board_name

New kernel linux-wandboard version 4.1.15_1.1.0_ga changed device tree
name adding board revision on file name. The new names are:

 - imx6dl-wandboard-revb1
 - imx6dl-wandboard-revc1
 - imx6q-wandboard-revb1
 - imx6q-wandboard-revc1

This fixes the Wandboard C1 revision device tree files.

Signed-off-by: Fabio Berton <fabio.berton@ossystems.com.br>
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>