package/libevas-generic-loaders: move to package directory

As for expedite package, there is no advantage for efl related
packages to share the same version number anymore
(except for efl and libelementary).

Also, we usually do not have a sub-directory for a family of related
packages which doen't share the same version number, so move
libevas-generic-loaders to package directory.
Libevas-generic-loaders appear now in "Libraries" -> "Graphics" in
the Kconfig menu.

Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>