i2c: Make I2C available on UML

Remove the global dependency of the I2C subsystem on HAS_IOMEM and
move the dependency to the i2c/busses submenu, with an exception for
i2c-stub.

The generic I2C part does not need to have HAS_IOMEM set and thus now
becomes available in UML, so the I2C subsystem can now be used, e.g.
by the i2c-stub driver, for development of I2C device drivers.

[JD: Some adjustments.]

[Heiko Carstens: Keep I2C disabled on S390.]

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 42d9fdd..8eed054 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -3,6 +3,7 @@
 #
 
 menu "I2C Hardware Bus support"
+	depends on HAS_IOMEM
 
 comment "PC SMBus host controller drivers"
 	depends on PCI
@@ -849,19 +850,6 @@
 	help
 	  Supports the SiByte SOC on-chip I2C interfaces (2 channels).
 
-config I2C_STUB
-	tristate "I2C/SMBus Test Stub"
-	depends on EXPERIMENTAL && m
-	default 'n'
-	help
-	  This module may be useful to developers of SMBus client drivers,
-	  especially for certain kinds of sensor chips.
-
-	  If you do build this module, be sure to read the notes and warnings
-	  in <file:Documentation/i2c/i2c-stub>.
-
-	  If you don't know what to do here, definitely say N.
-
 config SCx200_I2C
 	tristate "NatSemi SCx200 I2C using GPIO pins (DEPRECATED)"
 	depends on SCx200_GPIO