This function returns the first child object, but the returned pointer
is not compatible with (ConfigItem *).

Commit cc1c08ed ("kconfig: qconf: don't show goback button on
splitMode") uncovered this issue because using the pointer from this
function would make qconf crash. (https://lkml.org/lkml/2020/7/18/411)

This function does not work. Remove.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>