gallium: add PIPE_CAP_TGSI_PACK_HALF_FLOAT to indicate UP2H/PK2H support

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>
diff --git a/src/gallium/drivers/virgl/virgl_screen.c b/src/gallium/drivers/virgl/virgl_screen.c
index 668f2e0..0418cbb 100644
--- a/src/gallium/drivers/virgl/virgl_screen.c
+++ b/src/gallium/drivers/virgl/virgl_screen.c
@@ -220,6 +220,7 @@
    case PIPE_CAP_SHAREABLE_SHADERS:
    case PIPE_CAP_CLEAR_TEXTURE:
    case PIPE_CAP_DRAW_PARAMETERS:
+   case PIPE_CAP_TGSI_PACK_HALF_FLOAT:
       return 0;
    case PIPE_CAP_VENDOR_ID:
       return 0x1af4;