clk: qcom: common: Fix NULL vs IS_ERR() check in qcom_cc_icc_register()

The devm_clk_hw_get_clk() function doesn't return NULL, it returns error
pointers.  Update the checking to match.

Fixes: 8737ec83 ("clk: qcom: common: Add interconnect clocks support")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Imran Shaik <imran.shaik@oss.qualcomm.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/aLaPwL2gFS85WsfD@stanley.mountain


Signed-off-by: Bjorn Andersson <andersson@kernel.org>