uboot-imx

mx6: Distinguish mx6dual from mx6quad

Currently when we boot a mx6dual U-boot reports that it is a mx6quad.

Report it as MX6D instead:

CPU:   Freescale i.MX6D rev1.2 at 792 MHz

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Stefano babic <sbabic@denx.de>
Acked-by: Otavio Salvador <otavio@ossystems.com.br>