firmware: imx: fix coverity issue in ele-mu

commit 66e442bc7fdcc935e6faa94c743f653263d4ed67 from
https://github.com/nxp-imx/linux-imx.git



Fix the coverity issue: 30718543, found in the
EdgeLock Enclave MU driver.

Signed-off-by: Pankaj Gupta <pankaj.gupta@nxp.com>
Signed-off-by: Xiaolei Wang <xiaolei.wang@windriver.com>