imx: Add a common way for detecting NXP boards revision

NXP development boards based on i.MX6/i.MX7 contain the board
revision information stored in the fuses.

Introduce a common function that can be shared by different boards and
convert mx6sabreauto to use this new mechanism.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
5 files changed