rtc: rewrite isl1208 to support DM

Adds devicemodel support to the ISL1208 driver.
This patch drops the non-dm API as no board was using it anyway.
Also add it to Kconfig.

Signed-off-by: Klaus Goger <klaus.goger@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 95ac031..277dc3d 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -30,6 +30,18 @@
 	  Support for Dallas Semiconductor (now Maxim) DS1307 and DS1338/9 and
 	  compatible Real Time Clock devices.
 
+config RTC_ISL1208
+	bool "Enable ISL1208 driver"
+	depends on DM_RTC
+	help
+	  The Renesas (formerly Intersil) ISL1208 is a I2C Real Time Clock (RTC) and
+	  calendar with automatic leap year correction, 2-byte battery backed SRAM,
+	  automatic power switch-over, alarm function and 15 selectable frequency
+	  outputs.
+
+	  This driver supports reading and writing the RTC/calendar and detects
+	  total power failures.
+
 config RTC_RX8010SJ
 	bool "Enable RX8010SJ driver"
 	depends on DM_RTC