pulseaudio: use stricter PACKAGES_DYNAMIC

* I don't see any usage for libpulse-* packages
* adding '-' resolves the issue when we have separate recipe for
  pulseaudio-modules-droid which isn't built to satisfy RDEPENDS
  with the same name, because generic pulseaudio recipe seems to
  RPROVIDE it through PACKAGES_DYNAMIC

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>