mfd: Remove ARCH_U8500 dependency from AB8500

While it is vanishingly unlikely that the device will be deployed on other
architectures removing the dependency facilitates build testing when doing
generic work on both the MFD core for the device and the subsystem drivers.

There appears to be no actual code dependency.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/Kconfig

@@ -496,7 +496,7 @@ config EZX_PCAP
 
 config AB8500_CORE
 	bool "ST-Ericsson AB8500 Mixed Signal Power Management chip"
-	depends on GENERIC_HARDIRQS && ABX500_CORE && SPI_MASTER && ARCH_U8500
+	depends on GENERIC_HARDIRQS && ABX500_CORE && SPI_MASTER
 	select MFD_CORE
 	help
 	  Select this option to enable access to AB8500 power management