gst-plugins-bad: element selection rationalisation

gst-plugins-bad: element selection rationalisation

Using --with-plugins means you only get the elements you enable, so we were
dropping vast numbers of useful plugins such as the MPEG muxers.

Instead, follow gst-plugins-base by using PACKAGECONFIG to enable/disable
plugins with optional dependencies.

(From OE-Core rev: 7722fd48995d5d430d58b94ecf69a6ad9f1c741b)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>