[pxa3xx] reject unsupported combinations of blitting flags
[pxa3xx] reject unsupported combinations of blitting flags

Blitting with DSBLIT_BLEND_COLORALPHA is only accelerated if it is
not combined with other flags.

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