mfd: twl-core: Use the lookup table to find the correct subchip for the modules

Instead of using SUB_CHIP_ID* or magic numbers use the twl_mapping table to
look for the subchip ID.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>