timekeeping: Include the correct header for errno definitions

asm-generic headers are only defaults for architectures.  We need to get
the proper defintion, which goes through <linux/errno.h> and <asm/errno.h>.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: john.stultz@linaro.org
Link: http://lkml.kernel.org/r/1474555697-8206-1-git-send-email-hch@lst.deSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/timekeeping.h

 #ifndef _LINUX_TIMEKEEPING_H
 #define _LINUX_TIMEKEEPING_H
 
-#include <asm-generic/errno-base.h>
+#include <linux/errno.h>
 
 /* Included from linux/ktime.h */