Currently the config options CONFIG_SYS_DFU_DATA_BUF_SIZE and
CONFIG_SYS_DFU_MAX_FILE_SIZE are being set in include/configs/<board>.h
files and also in <board_name>_defconfig files without a Kconfig option. It
is easier for users to set these configs in defconfig files than in config
header files as they are a part of the source code.

Add Kconfig symbols, and update the defconfigs by using tools/moveconfig.py
script.
Suggested-by: NPratyush Yadav <p.yadav@ti.com>
Signed-off-by: NAswath Govindraju <a-govindraju@ti.com>
Acked-by: NOleksandr Suvorov <oleksandr.suvorov@toradex.com>
Acked-by: NMatthias Brugger <mbrugger@suse.com>
Acked-by: NLukasz Majewski <lukma@denx.de>