habanalabs: improve utilization calculation

The new approach is based on the notion that the relative
current power consumption is in relation of proportionality
to device's true utilization.
Utilization info ranges between [0,100]%
Currently, dc_power values are hard-coded.

Signed-off-by: Koby Elbaz <kelbaz@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>