ARM: configs: at91: add defconfig for sama7 family of SoCs

Add defconfig for sama7 SoC family.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
[claudiu.beznea@microchip.com: add clocks, ethernet, timers, power]
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
[codrin.ciubotariu@microchip.com: add audio]
Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
[nicolas.ferre@microchip.com: atags not set, mtd tests, spi gpio]
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20210628120452.74408-3-eugen.hristev@microchip.com