mfd: twl6040: Rename the core driver

After the regmap_irq conversion there is no need to call the driver
as twl6040-core.c since there is only one c file remained.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 05bebf6..8a68fc7 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -67,7 +67,7 @@
 obj-$(CONFIG_TWL4030_MADC)      += twl4030-madc.o
 obj-$(CONFIG_TWL4030_POWER)    += twl4030-power.o
 obj-$(CONFIG_MFD_TWL4030_AUDIO)	+= twl4030-audio.o
-obj-$(CONFIG_TWL6040_CORE)	+= twl6040-core.o
+obj-$(CONFIG_TWL6040_CORE)	+= twl6040.o
 
 obj-$(CONFIG_MFD_MC13XXX)	+= mc13xxx-core.o
 obj-$(CONFIG_MFD_MC13XXX_SPI)	+= mc13xxx-spi.o