imx: ocotp: mxc add i.MX7D support

* Ocotp of i.MX7D has different operation rule.
  This patch is to add support for i.MX7D ocotp.

Signed-off-by: Adrian Alonso <aalonso@freescale.com>
Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Signed-off-by: Ye.Li <B37916@freescale.com>