mfd: atmel-flexcom: Add a driver for Atmel Flexible Serial Communication Unit

This driver supports the new Atmel Flexcom. The Flexcom is a wrapper which
integrates one SPI controller, one I2C controller and one USART. Only one
function can be enabled at a time. This driver selects the function once
for all, when the Flexcom is probed, according to the value of the new
"atmel,flexcom-mode" device tree property.

This driver has chosen to present the Flexcom to the system as a MFD so
the implementation is seamless for the existing Atmel SPI, I2C and USART
drivers.

Also the Flexcom embeds FIFOs: the latest patches of the SPI, I2C and
USART drivers take advantage of this new feature.

Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index d6c21e3..a8b76b8 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -164,6 +164,7 @@
 obj-$(CONFIG_TPS65911_COMPARATOR)	+= tps65911-comparator.o
 obj-$(CONFIG_MFD_TPS65090)	+= tps65090.o
 obj-$(CONFIG_MFD_AAT2870_CORE)	+= aat2870-core.o
+obj-$(CONFIG_MFD_ATMEL_FLEXCOM)	+= atmel-flexcom.o
 obj-$(CONFIG_MFD_ATMEL_HLCDC)	+= atmel-hlcdc.o
 obj-$(CONFIG_MFD_INTEL_LPSS)	+= intel-lpss.o
 obj-$(CONFIG_MFD_INTEL_LPSS_PCI)	+= intel-lpss-pci.o