drm/mga/mga_ioc32: Fix some formatting issues in 'mga_compat_ioctl's header

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/mga/mga_ioc32.c:171: warning: Function parameter or member 'filp' not described in 'mga_compat_ioctl'
 drivers/gpu/drm/mga/mga_ioc32.c:171: warning: Function parameter or member 'cmd' not described in 'mga_compat_ioctl'
 drivers/gpu/drm/mga/mga_ioc32.c:171: warning: Function parameter or member 'arg' not described in 'mga_compat_ioctl'

Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210115181313.3431493-7-lee.jones@linaro.org

drivers/gpu/drm/mga/mga_ioc32.c

@@ -159,13 +159,13 @@ static struct {
 };
 
 /**
- * Called whenever a 32-bit process running under a 64-bit kernel
- * performs an ioctl on /dev/dri/card<n>.
+ * mga_compat_ioctl - Called whenever a 32-bit process running under
+ *                    a 64-bit kernel performs an ioctl on /dev/dri/card<n>.
  *
- * \param filp file pointer.
- * \param cmd command.
- * \param arg user argument.
- * \return zero on success or negative number on failure.
+ * @filp: file pointer.
+ * @cmd:  command.
+ * @arg:  user argument.
+ * return: zero on success or negative number on failure.
  */
 long mga_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {