regulator: rc5t583: Remove nsteps from struct rc5t583_regulator_info

The nsteps can be calculated by (_max_mv - _min_mv) * 1000 / _step_uV + 1,
thus we can remove _nsteps from RC5T583_REG macro, and then remove
nsteps from struct rc5t583_regulator_info.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>