kconfig: qconf: cleanup includes

The usage of c-like include is deprecated on modern Qt
versions. Use the c++ style includes.

While here, remove uneeded and redundant ones, sorting
them on alphabetic order.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>