ARM: at91/defconfig: remove CONFIG_SYSFS_DEPRECATED

Recent distributions and userspace tools after 2009/2010 depend on
the existence of /sys/class/block/, and will not work with this option enabled.

Signed-off-by: Anthony Harivel <anthony.harivel@emtrion.de>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>