PM: AVS: qcom-cpr: Use nvmem_cell_read_variable_le_u32()

PM: AVS: qcom-cpr: Use nvmem_cell_read_variable_le_u32()

Let's delete the private function cpr_read_efuse() since it does the
basically the same thing as the new API call
nvmem_cell_read_variable_le_u32().

Differences between the new API call and the old private function:
* less error printing (I assume this is OK).
* will give an error if the value doesn't fit in 32-bits (the old code
  would have truncated silently).

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Niklas Cassel <nks@flawful.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20210521134437.v2.1.Id1c70158722750aec0673d60c12e46a9c66bbfed@changeid
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>