include/linux/iopoll.h: include <linux/ktime.h> instead of <linux/hrtimer.h>

The timer APIs this header needs are ktime_get(), ktime_add_us(), and
ktime_compare().  So, including <linux/ktime.h> seems enough.  This
commit will cut unnecessary header file parsing.

Link: http://lkml.kernel.org/r/1481679225-10885-1-git-send-email-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/iopoll.h

@@ -17,7 +17,7 @@
 
 #include <linux/kernel.h>
 #include <linux/types.h>
-#include <linux/hrtimer.h>
+#include <linux/ktime.h>
 #include <linux/delay.h>
 #include <linux/errno.h>
 #include <linux/io.h>