configs: Add sam9x60ek_mmc_defconfig

configs: Add sam9x60ek_mmc_defconfig

add sam9x60ek_mmc_defconfig and for now only supports booting from
sdcard.

Signed-off-by: Sandeep Sheriker Mallikarjun <sandeepsheriker.mallikarjun@microchip.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
[nicolas.ferre@microchip.com: split patch, add Ethernet controller,
phy and tools]
[claudiu.beznea@microchip.com: add CONFIG_OF_LIBFDT_OVERLAY]
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
[tudor.ambarus@microchip.com: Fix number of DRAM banks:
One DDR2-SDRAM (W972GG6KB 2 Gbit = 16 Mbit x 16 x 8 banks]
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>