eglibc-locale: add eglibc-gconv to PACKAGES_DYNAMIC

eglibc-locale: add eglibc-gconv to PACKAGES_DYNAMIC

If you try to add eglibc-gconv to an image, you'll get a NoProvider
error because nothing at parse time states that it provides this (it's
added to PACKAGES in populate_packages). This problem manifests itself
in Hob for example when customising an image.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>