soc: qcom: smd: Use __iowrite32_copy() instead of open-coding it

We already have a function to do this and it silences some sparse
warnings along the way.

Reviewed-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Andy Gross <agross@codeaurora.org>