mfd: mt6360: Rename mt6360_pmu_data by mt6360_ddata

Rename mt6360_pmu_data by mt6360_ddata because of including
not only PMU part, but also entire MT6360 IC.

Signed-off-by: Gene Chen <gene_chen@richtek.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>