net: ag71xx: Add missing header

ag71xx uses devm_ioremap_nocache. This fixes usage of an implicit function

Fixes: d51b6ce4 ("net: ethernet: add ag71xx driver")
Signed-off-by: Rosen Penev <rosenp@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/atheros/ag71xx.c

@@ -35,6 +35,7 @@
 #include <linux/regmap.h>
 #include <linux/reset.h>
 #include <linux/clk.h>
+#include <linux/io.h>
 
 /* For our NAPI weight bigger does *NOT* mean better - it means more
  * D-cache misses and lots more wasted cycles than we'll ever