i2c: Only build Tyan SMBus mux drivers on x86

The two Tyan SMBus mux drivers (i2c-amd756-s4882 and i2c-nforce2-s4985)
are only useful on specific x86 motherboards, so there is no point in
letting them be built on other architectures.
Signed-off-by: NJean Delvare <khali@linux-fr.org>

drivers/i2c/busses/Kconfig

@@ -55,7 +55,7 @@ config I2C_AMD756
 
 config I2C_AMD756_S4882
 	tristate "SMBus multiplexing on the Tyan S4882"
-	depends on I2C_AMD756 && EXPERIMENTAL
+	depends on I2C_AMD756 && X86 && EXPERIMENTAL
 	help
 	  Enabling this option will add specific SMBus support for the Tyan
 	  S4882 motherboard.  On this 4-CPU board, the SMBus is multiplexed
@@ -148,7 +148,7 @@ config I2C_NFORCE2
 
 config I2C_NFORCE2_S4985
 	tristate "SMBus multiplexing on the Tyan S4985"
-	depends on I2C_NFORCE2 && EXPERIMENTAL
+	depends on I2C_NFORCE2 && X86 && EXPERIMENTAL
 	help
 	  Enabling this option will add specific SMBus support for the Tyan
 	  S4985 motherboard.  On this 4-CPU board, the SMBus is multiplexed