mfd: Remove default selection of AB4500

This remove the default 'y' selection of AB4500, currently everyone
enabling the SPI subsystem will get a copy of this driver.
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Cc: Srinidhi Kasagar <srinidhi.kasagar@stericsson.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/Kconfig

@@ -342,7 +342,6 @@ config MFD_88PM8607
 config AB4500_CORE
 	tristate "ST-Ericsson's AB4500 Mixed Signal Power management chip"
 	depends on SPI
-	default y
 	help
 	  Select this option to enable access to AB4500 power management
 	  chip. This connects to U8500 on the SSP/SPI bus and exports