arm: at91: configs: Enable CONFIG_SYS_NAND_USE_FLASH_BBT on all boards

arm: at91: configs: Enable CONFIG_SYS_NAND_USE_FLASH_BBT on all boards

As highlighted by Stefan in the commit acf252ef6295 ("arm: at91:
gardena-smart-gateway-at91sam: Enable CONFIG_SYS_NAND_USE_FLASH_BBT")
it's important to use BBT when Linux enables it. We use it for a long
time on all our boards.

Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Stefan Roese <sr@denx.de>
Cc: Eugen Hristev <eugen.hristev@microchip.com>
Cc: Tom Rini <trini@konsulko.com>
Acked-by: Alexander Dahl <ada@thorsis.com>