rtc: Add an RTC driver for the AS3722 PMIC.

The AS3722 PMIC, like many PMICs, has an RTC built into it. This change adds a
driver for it which implements the new RTC API.

BUG=None
TEST=Built and booted with the event log code modified to use this interface.
Verified that events had accurate timestamps.
BRANCH=nyan

Original-Change-Id: I400adccbf84221dcba8d520276bb91b389f72268
Original-Signed-off-by: Gabe Black <gabeblack@google.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/197796
Original-Reviewed-by: Gabe Black <gabeblack@chromium.org>
Original-Tested-by: Gabe Black <gabeblack@chromium.org>
Original-Commit-Queue: Gabe Black <gabeblack@chromium.org>
(cherry picked from commit 011e49beba3a99abbd122866891e3c20bf1188d2)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: Ibc1d342062c7853a30d195496c077e37a02b35b0
Reviewed-on: http://review.coreboot.org/7890
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
diff --git a/src/drivers/Makefile.inc b/src/drivers/Makefile.inc
index 7ae3eb2..151e3f7 100644
--- a/src/drivers/Makefile.inc
+++ b/src/drivers/Makefile.inc
@@ -17,6 +17,7 @@
 ## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 ##
 
+subdirs-y += ams
 subdirs-y += ati
 subdirs-y += dec
 subdirs-y += emulation