package/opengl/libopenmax: switch to package-defined providers

package/opengl/libopenmax: switch to package-defined providers

For the underlying reasons, see previous patch, titled:
    package/opengl/libegl: switch to package-defined providers

Reported-by: David Corvoysier <david.corvoysier@orange.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Peter Korsgaard <jacmet@uclibc.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>