mfd: Add mc13892 support to mc13xxx

mc13892 is the companion PMIC for Freescale's i.MX51.  It's similar enough
to mc13782 to support it in a single driver.

This patch introduces enough compatibility cruft to keep all users of the
superseded mc13783 driver unchanged.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 9735f58..6c6b9f0 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -409,11 +409,16 @@
 	  so that function-specific drivers can bind to them.
 
 config MFD_MC13783
-	tristate "Support Freescale MC13783"
+	tristate
+
+config MFD_MC13XXX
+	tristate "Support Freescale MC13783 and MC13892"
 	depends on SPI_MASTER
 	select MFD_CORE
+	select MFD_MC13783
 	help
-	  Support for the Freescale (Atlas) MC13783 PMIC and audio CODEC.
+	  Support for the Freescale (Atlas) PMIC and audio CODECs
+	  MC13783 and MC13892.
 	  This driver provides common support for accessing  the device,
 	  additional drivers must be enabled in order to use the
 	  functionality of the device.