[PATCH] drm/mipi-dsi: Fix detach call without attach

[H. Nikolaus Schaller]

Hi,
I have tested this on an OMAP5 Pyra.

> Am 21.09.2023 um 12:50 schrieb Tomi Valkeinen <tomi.valkeinen at ideasonboard.com>:
> 
> It's been reported that DSI host driver's detach can be called without
> the attach ever happening:
> 
> https://lore.kernel.org/all/20230412073954.20601-1-tony@atomide.com/
> 

This patch works equally well as my proposal and is indeed a better solution
(solving the issue and not just suppressing a warning).

Tested-by: H. Nikolaus Schaller <hns at goldelico.com>

BR and thanks,
Nikolaus