soc: qcom: rpmpd: use correct __le32 type

Use cpu_to_le32 to cast constants to __le32 before comparing
them with __le32 type pd->key. This fixes the following sparse
warnings:

drivers/soc/qcom/rpmpd.c:895:31: sparse: warning: restricted __le32 degrades to integer
drivers/soc/qcom/rpmpd.c:896:15: sparse: warning: restricted __le32 degrades to integer

Signed-off-by: Min-Hua Chen <minhuadotchen@gmail.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230522160757.284165-1-minhuadotchen@gmail.com