kconfig

Re-sync all files under the scripts/kconfig directory with
Linux 4.10.

Some parts include U-Boot own modification.  I made sure to not
revert the following commits:

 5b8031cc ("Add more SPDX-License-Identifier tags")
 192bc694 ("Fix GCC format-security errors and convert sprintfs.")
 da58dec8 ("Various Makefiles: Add SPDX-License-Identifier tags")
 20c20826 ("Kconfig: Enable usage of escape char '\' in string values")

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>