sama5d3: support sama5d36 chip

Signed-off-by: Josh Wu <josh.wu@atmel.com>
at91: change default bootcmd to bootz, which to load zImage kernel

change boards includes: at91sam9m10g45ek, at91sam9n12ek, at91sam9x5ek
and sama5d3xek.

Signed-off-by: Josh Wu <josh.wu@atmel.com>
at91sam9g20: change default bootcmd to bootz, which to load zImage.

Signed-off-by: Josh Wu <josh.wu@atmel.com>