net: caif: remove unused hardirq.h

Preempt counter APIs have been split out, currently, hardirq.h just
includes irq_enter/exit APIs which are not used by caif at all.

So, remove the unused hardirq.h.
Signed-off-by: Yang Shi <yang.s@alibaba-inc.com>
Cc: Dmitry Tarnyagin <dmitry.tarnyagin@lockless.no>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/caif/cfpkt_skbuff.c

@@ -8,7 +8,6 @@
 
 #include <linux/string.h>
 #include <linux/skbuff.h>
-#include <linux/hardirq.h>
 #include <linux/export.h>
 #include <net/caif/cfpkt.h>
 

net/caif/chnl_net.c

@@ -8,7 +8,6 @@
 #define pr_fmt(fmt) KBUILD_MODNAME ":%s(): " fmt, __func__
 
 #include <linux/fs.h>
-#include <linux/hardirq.h>
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/netdevice.h>