gallium: add PIPE_CAP_DRAW_PARAMETERS

This allows the state tracker to know that the various draw parameters
are available in vertex shaders.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
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 26a4f77..668f2e0 100644
--- a/src/gallium/drivers/virgl/virgl_screen.c
+++ b/src/gallium/drivers/virgl/virgl_screen.c
@@ -219,6 +219,7 @@
    case PIPE_CAP_FORCE_PERSAMPLE_INTERP:
    case PIPE_CAP_SHAREABLE_SHADERS:
    case PIPE_CAP_CLEAR_TEXTURE:
+   case PIPE_CAP_DRAW_PARAMETERS:
       return 0;
    case PIPE_CAP_VENDOR_ID:
       return 0x1af4;