panfrost: Enable 2 sample count support on v12+

v12+ supports this, let's expose it.

Signed-off-by: Mary Guillemard <mary.guillemard@collabora.com>
Reviewed-by: Eric R. Smith <eric.smith@collabora.com>
Reviewed-by: Olivia Lee <olivia.lee@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34997>

src/gallium/drivers/panfrost/pan_screen.c

@@ -156,6 +156,11 @@ panfrost_is_format_supported(struct pipe_screen *screen,
    case 1:
    case 4:
       break;
+   case 2:
+      if (dev->arch >= 12)
+         break;
+      else
+         return false;
    case 8:
    case 16:
       if (dev->debug & PAN_DBG_MSAA16)