xconfig: Fix the filename for GUI settings

Currently the qconf program invoked by 'make xconfig' stores GUI
settings in the file ~/.config/Unknown\ Organization.conf.  This name
is apparently generated by the QSettings class when no organisation
or application name are specified.

This is obviously not a sensible filename (nor does it seem sensible
that these QSettings parameters are optional!).  Pass the names
'kernel.org' and 'qconf', resuling in the filename
~/.config/kernel.org/qconf.conf.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>