usb: dfu: Migrate CONFIG_SYS_DFU_DATA_BUF_SIZE and CONFIG_SYS_DFU_MAX_FILE_SIZE to Kconfig

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: Pratyush Yadav <p.yadav@ti.com>
Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>
Acked-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
Acked-by: Matthias Brugger <mbrugger@suse.com>
Acked-by: Lukasz Majewski <lukma@denx.de>
diff --git a/configs/pico-pi-imx6ul_defconfig b/configs/pico-pi-imx6ul_defconfig
index 7d9e219..06fa449 100644
--- a/configs/pico-pi-imx6ul_defconfig
+++ b/configs/pico-pi-imx6ul_defconfig
@@ -44,6 +44,7 @@
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
 CONFIG_BOUNCE_BUFFER=y
 CONFIG_DFU_MMC=y
+CONFIG_SYS_DFU_DATA_BUF_SIZE=0x1000000
 CONFIG_USB_FUNCTION_FASTBOOT=y
 CONFIG_FASTBOOT_BUF_SIZE=0x10000000
 CONFIG_FASTBOOT_FLASH=y