MLK-19767-1: imx7ulp: configs: Enable DEFAULT_FDT_FILE

MLK-19767-1: imx7ulp: configs: Enable DEFAULT_FDT_FILE

Specify the default dtb file for kernel boot per i.MX7ULP
board config.

Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
Reviewed-by: Frank Li <Frank.li@nxp.com>
Reviewed-by: Ye Li <ye.li@nxp.com>
(cherry picked from commit 3fba1c1a76cadfe0177e61a85eac3da10ee086e0)
(cherry picked from commit 013eb1fdfdb33df19a0917fd554160a84ec45dd1)
(cherry picked from commit 6052c4d6059f7f545f2f6d73bf77dd4fc5687130)
(cherry picked from commit 25bc40364344a414282c16052d044f7000c94aa8)
(cherry picked from commit 734368dc183a9d8e3b9fb46d30dac5efe4639556)