SECURE_BOOT: Correct reading of ITS bit

The ITS bit was being read incorrectly beacause of operator
precedence. The same ahs been corrected.

Signed-off-by: Lawish Deshmukh <lawish.deshmukh@freescale.com>
Signed-off-by: Aneesh Bansal <aneesh.bansal@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>