rtph264pay: force baseline profile is profile-level-id is unspecified
rtph264pay: force baseline profile is profile-level-id is unspecified

If profile-level-id is missing or invalid, we want any upstream
encoder to default to baseline profile, so specify that in the
caps we pass upstream. If the caps contain no profile restriction,
an encoder may default to high or main profile.

matsu/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer-sdk__gst-plugins-good,matsu/gst-plugins-good,matsu/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer-sdk__gst-plugins-good,freedesktop-unofficial-mirror/gstreamer-sdk__gst-plugins-good,matsu/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer-sdk__gst-plugins-good