[iwlwifi] Compile error by 'linux/iopoll.h'

From: Takashi Inoue via freebsd-wireless <freebsd-wireless_at_FreeBSD.org>
Date: Fri, 29 Oct 2021 07:54:04 UTC
Hi All,

Today, I  tried to test the iwlwifi driver at 
https://wiki.freebsd.org/WiFi/Iwlwifi,
but I could not rebuild a kernel as follows.

--------------------------------------------------------
In file included from /usr/src/sys/dev/rtw88/main.c:11:
/usr/src/sys/dev/rtw88/main.h:14:10: fatal error: 'linux/iopoll.h' file 
not found
#include <linux/iopoll.h>
          ^~~~~~~~~~~~~~~~
1 error generated.
*** Error code 1
---------------------------------------------------------

My system source is 13.0-STABLE snapshot at 2021-Oct-14.
I used MYKERNEL which is a copy of GENERIC.

How can I overcome this?  Please help me.

Thanks,
Takashi Inoue