LF-5453 firmware: Makefile to include seco-mu driver

commit b69fe99023a80cb17604e36049ad7b41a538bf2e from
https://source.codeaurora.org/external/imx/linux-imx

Changes done Makefile:
- include back the seco driver

Fixes: 2601f7ac2409 ("Nomenclature changes from sentinel to ele")
Signed-off-by: Pankaj Gupta <pankaj.gupta@nxp.com>
Signed-off-by: Xiaolei Wang <xiaolei.wang@windriver.com>