package/pipewire: add missing dependencies/plugins

package/pipewire: add missing dependencies/plugins

Added missing required and optional dependencies.
Provide option to enable gstreamer plugin.

Fixes:

  http://autobuild.buildroot.net/results/9671ad63b1ae147a6f660337cb4b3dc38209067c/
  http://autobuild.buildroot.net/results/0e80841fe9937d7a5142035c2a41158166bcf8df/

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
[Thomas:
 - enclose new option in if ... endif block
 - add missing Config.in comment
 - add dependency on gstreamer1 in .mk file]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>