qtfeeback currently has a hard dependency on qtmultimedia. qtfeedback
only uses multimedia in the mmk plugin. This change modifies the build
system only as all the required infrastructure changes in qtfeedback
are already present.

Change-Id: Ie9884dfd51fb040cde3e29247f1f51ea7f0bd637
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>
Reviewed-by: Sergio Ahumada <sergio.ahumada@nokia.com>