vcomp/cmpto_j2k: support RG48

RG48 can be supported immediately, see also the commit d0832b5e (similar
change for the decoder).

src/video_compress/cmpto_j2k.cpp

@@ -184,6 +184,7 @@ static struct {
         {RGB, CMPTO_444_U8_P012, VIDEO_CODEC_NONE, nullptr},
         {RGBA, CMPTO_444_U8_P012Z, VIDEO_CODEC_NONE, nullptr},
         {R10k, CMPTO_444_U10U10U10_MSB32BE_P210, VIDEO_CODEC_NONE, nullptr},
+        {RG48, CMPTO_444_U12_MSB16LE_P012, VC_NONE, nullptr},
         {R12L, CMPTO_444_U12_MSB16LE_P012, RG48, r12l_to_rg48_cuda},
 };