kconfig: qconf: Change title for the item window

Both main config window and the item window have "Option"
name. That sounds weird, and makes harder to debug issues
of a window appearing at the wrong place.

So, change the title to reflect the contents of each
window.

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