vapostproc: Do not append ANY caps into pad template
The ANY caps in pad template caps seems to mess up the DMA negotiation. The command of:
GST_GL_API=opengl gst-launch-1.0 -vf videotestsrc ! video/x-raw,format=NV12 ! vapostproc ! "video/x-raw(memory:DMABuf)" ! glimagesink
fails to negotiate, but in fact, the vapostproc can convert the input NV12 formant into the RGBA format to render.
The ANY may help the passthough mode, but we should make the negotiate correct first.