package/qt: Fix Kconfig for OpenGL support

package/qt: Fix Kconfig for OpenGL support

BR2_PACKAGE_QT_OPENGL_ES was moved to a choice option. This option kind
can apparently not be selected by other packages. Therefore this patch
introduces a new Kconfig option BR2_PACKAGE_QT_OPENGL which takes care
of OpenGL support as such, BR2_PACKAGE_QT_OPENGL_NONE is not needed
anymore now. The choice options are now only used to determine the
type of OpenGL support.

This patch contains the necessary preparation to fix a build error in
the qwt package.

[Peter: fix QT_OPENGL dependencies to match options]
Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>