i915g: we also have more than 0 viewports!

See 546d6c8d for the corresponding fix in freedreno.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Stephane Marchesin <stephane.marchesin@gmail.com>
Cc: "10.3" <mesa-stable@lists.freedesktop.org>

src/gallium/drivers/i915/i915_screen.c

@@ -240,6 +240,9 @@ i915_get_param(struct pipe_screen *screen, enum pipe_cap cap)
    case PIPE_CAP_SAMPLER_VIEW_TARGET:
       return 0;
 
+   case PIPE_CAP_MAX_VIEWPORTS:
+      return 1;
+
    case PIPE_CAP_MIN_MAP_BUFFER_ALIGNMENT:
       return 64;