generic: fixes for big-endian handling for NV12/NV16/NV21
generic: fixes for big-endian handling for NV12/NV16/NV21

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