soc: qcom: stats: Add DDR sleep stats

soc: qcom: stats: Add DDR sleep stats

Add DDR sleep stats that include:

- the available RAM low power states
- per-state residency information
- per-frequency residency information (for some freqs only, it seems)
- DDR vote information (AB/IB)

and some magic thing that we're yet to decode.

Based on the msm-5.4 downstream implementation, debugged with some help
from Qualcomm's Maulik Shah.

Signed-off-by: Konrad Dybcio <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[bjorn: Add missing bitfield.h include]
Signed-off-by: Bjorn Andersson <[email protected]>