convert: fix (A)VYU conversion to RGB24 and RGB16
convert: fix (A)VYU conversion to RGB24 and RGB16

Signed-off-by: André Draszik <4a4cb09e7b43b167f95b1dc166b9a7dec9f65d7c@st.com>

kevleyski/DirectFB-1,jcdubois/DirectFB,dfbdok/DirectFB1,kevleyski/directfb,lancebaiyouview/DirectFB,sklnet/DirectFB,sklnet/DirectFB,deniskropp/DirectFB,sklnet/DirectFB,kevleyski/DirectFB-1,kevleyski/directfb,djbclark/directfb-core-DirectFB,mtsekm/test,sklnet/DirectFB,deniskropp/DirectFB,deniskropp/DirectFB,mtsekm/test,DirectFB/directfb,deniskropp/DirectFB,kaostao/directfb,lancebaiyouview/DirectFB,Distrotech/DirectFB,lancebaiyouview/DirectFB,DirectFB/directfb,dfbdok/DirectFB1,jcdubois/DirectFB,djbclark/directfb-core-DirectFB,DirectFB/directfb,djbclark/directfb-core-DirectFB,djbclark/directfb-core-DirectFB,kevleyski/DirectFB-1,kaostao/directfb,Distrotech/DirectFB,kevleyski/directfb,mtsekm/test,lancebaiyouview/DirectFB,jcdubois/DirectFB,kaostao/directfb,dfbdok/DirectFB1,kevleyski/directfb,kevleyski/DirectFB-1,Distrotech/DirectFB