Fix on MAC setting in NVS file

Many HW platform will not allow accessing unsigned int values in odd
addresses, so you should pass to a sscanf with %x format a pointer to
a unsigned int value.  Bug detected on a Samsung's S3C2416 based
platform.

Signed-off-by: José Miguel Gonçalves <jose.goncalves@inov.pt>
Signed-off-by: Luciano Coelho <coelho@ti.com>