linux-phytec-ti

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>