timekeeping: Fix declaration of read_persistent_wall_and_boot_offset()

It is read_persistent_wall_and_boot_offset() and not
read_persistent_clock_and_boot_offset()

Fixes: 3eca9937 ("timekeeping: Replace read_boot_clock64() with read_persistent_wall_and_boot_offset()")
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
Link: https://lkml.kernel.org/r/20180903081533.34366-1-borntraeger@de.ibm.com

include/linux/timekeeping.h

@@ -258,7 +258,7 @@ extern void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot);
 extern int persistent_clock_is_local;
 
 extern void read_persistent_clock64(struct timespec64 *ts);
-void read_persistent_clock_and_boot_offset(struct timespec64 *wall_clock,
+void read_persistent_wall_and_boot_offset(struct timespec64 *wall_clock,
 					  struct timespec64 *boot_offset);
 extern int update_persistent_clock64(struct timespec64 now);