defconfig: Rename sama5d3xek loading android default configuration file name.

To follow the default configuration file name convention

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Config System: Add Long FileName(LFN) configuration options

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
FatFS: Add support to Long FileName(LFN)

Set the Maximum Long File Name(LFN) length to 32.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Board File: Add board respective device tree filename(dtb).

Due to add the FatFS Long FileName(LFN) support, add the board respective dtb filenamed.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
defconfig: update the sdcard default configuration file

Due to introduction the Long FileName(LFN) configuration options

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>