i2c-mpc: add support for the MPC512x processors from Freescale

As I2C interrupts must  be enabled for the MPC512x by the setup function
as well, "fsl,preserve-clocking" is handled in a slighly different way.
Also, the old settings are now reported calling dev_dbg(). For the
MPC512x the clock setup function of the MPC52xx can be re-used.
Furthermore, the Kconfig help has been updated and corrected.

Signed-off-by: Wolfgang Grandegger <wg@denx.de>
Reviewed-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 1004181..ecf079b 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -419,13 +419,12 @@
 	  instead.
 
 config I2C_MPC
-	tristate "MPC107/824x/85xx/52xx/86xx"
+	tristate "MPC107/824x/85xx/512x/52xx/83xx/86xx"
 	depends on PPC32
 	help
 	  If you say yes to this option, support will be included for the
-	  built-in I2C interface on the MPC107/Tsi107/MPC8240/MPC8245 and
-	  MPC85xx/MPC8641 family processors. The driver may also work on 52xx
-	  family processors, though interrupts are known not to work.
+	  built-in I2C interface on the MPC107, Tsi107, MPC512x, MPC52xx,
+	  MPC8240, MPC8245, MPC83xx, MPC85xx and MPC8641 family processors.
 
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-mpc.