[S390] Use CONFIG_GENERIC_TIME and define TOD clock source.

Fix too slow clock by using CONFIG_GENERIC_TIME and adding a
clock source for the s390 time-of-day clock. As added benefit
we get rid of the s390 specific definition of do_gettimeofday
and do_settimeofday.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/defconfig b/arch/s390/defconfig
index b6cad75..a325739 100644
--- a/arch/s390/defconfig
+++ b/arch/s390/defconfig
@@ -9,6 +9,7 @@
 CONFIG_RWSEM_XCHGADD_ALGORITHM=y
 CONFIG_GENERIC_HWEIGHT=y
 CONFIG_GENERIC_CALIBRATE_DELAY=y
+CONFIG_GENERIC_TIME=y
 CONFIG_S390=y
 CONFIG_DEFCONFIG_LIST="/lib/modules/$UNAME_RELEASE/.config"