mtd: phram: fix asm/io.h include usage

Modify phram to include <linux/io.h> rather than <asm/io.h>
Signed-off-by: Rob Ward <robert.ward114@googlemail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/devices/phram.c

@@ -17,7 +17,7 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
-#include <asm/io.h>
+#include <linux/io.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/list.h>