power: rx51_battery: Fix reporting correct values

Tell twl4030_madc_conversion that this driver needs raw values.
Driver twl4030_madc has some hardcoded values and conversation
functions which are incorrect for Nokia RX-51 board. This driver
rx51_battery expects raw values which convert itself.

This patch fixing values reported by power supply interface.
Before this patch driver reported always incorrect values on
3.8 kernel (sometimes design capacity was negative).

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Acked-by: Anton Vorontsov <anton@enomsg.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>