drm/nouveau: don't misuse kernel-doc comments

Change kernel-doc "/**" comments to common "/*" comments to prevent
kernel-doc warnings:

nouveau_ioc32.c:2: warning: Cannot understand  * \file mga_ioc32.c
 on line 2 - I thought it was a doc line
nouveau_ioc32.c:52: warning: Function parameter or member 'filp' not described in 'nouveau_compat_ioctl'
nouveau_ioc32.c:52: warning: Function parameter or member 'cmd' not described in 'nouveau_compat_ioctl'
nouveau_ioc32.c:52: warning: Function parameter or member 'arg' not described in 'nouveau_compat_ioctl'
nouveau_ioc32.c:52: warning: expecting prototype for Called whenever a 32-bit process running under a 64(). Prototype was for nouveau_compat_ioctl() instead
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Karol Herbst <kherbst@redhat.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Danilo Krummrich <dakr@redhat.com>
Cc: nouveau@lists.freedesktop.org
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231231233633.6596-2-rdunlap@infradead.org

drivers/gpu/drm/nouveau/nouveau_ioc32.c

-/**
+/*
  * \file mga_ioc32.c
  *
  * 32-bit ioctl compatibility routines for the MGA DRM.
@@ -38,7 +38,7 @@
 
 #include "nouveau_ioctl.h"
 
-/**
+/*
  * Called whenever a 32-bit process running under a 64-bit kernel
  * performs an ioctl on /dev/dri/card<n>.
  *