qtopia4: add kconfig option to enable Phonon

This patch adds a kconfig option to enable Phonon when configuring Qt.

Phonon is the multimedia API from KDE 4 which has been integrated into
Qt 4.4. For playback under Linux the GStreamer multimedia framework is
used.

Signed-off-by: Markus Heidelberg <markus.heidelberg@web.de>
Signed-off-by: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>