kbd: upgrade 2.6.3 -> 2.6.4

Changelog:
==========
-Use AX_ADD_FORTIFY_SOURCE to avoid redefining _FORTIFY_SOURCE
-Do not look up include files in the current working directory

Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>