Pass to dev_err_probe() PTR_ERR from actual dev_pm_opp_find_bw_floor()
call which failed, instead of previous ret which at this point is 0.
Failure of dev_pm_opp_find_bw_floor() would result in prematurely ending
the probe with success.

Fixes smatch warnings:

  drivers/soc/qcom/icc-bwmon.c:776 bwmon_probe() warn: passing zero to 'dev_err_probe'
  drivers/soc/qcom/icc-bwmon.c:781 bwmon_probe() warn: passing zero to 'dev_err_probe'
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://lore.kernel.org/r/202305131657.76XeHDjF-lkp@intel.com/
Cc: <stable@vger.kernel.org>
Fixes: b9c2ae6c ("soc: qcom: icc-bwmon: Add bandwidth monitoring driver")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230513111747.132532-1-krzysztof.kozlowski@linaro.org