mfd: max77693: Allow building as a module

The consumer of max77693 regulators on Trats2 board (samsung-usb2-phy
driver) supports deferred probing so the max77693 main MFD driver can be
built now as a module. This gives more flexibility and removes manual
ordering of init calls.

Suggested-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index eea61e3..aa1e7c3 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -543,8 +543,8 @@
 	  of the device.
 
 config MFD_MAX77693
-	bool "Maxim Semiconductor MAX77693 PMIC Support"
-	depends on I2C=y
+	tristate "Maxim Semiconductor MAX77693 PMIC Support"
+	depends on I2C
 	select MFD_CORE
 	select REGMAP_I2C
 	select REGMAP_IRQ