remoteproc: qcom: q6v5-mss: Use regmap_read_poll_timeout

Replace the loop for HALT_ACK detection with regmap_read_poll_timeout.

Reviewed-by: Evan Green <evgreen@chromium.org>
Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
Link: https://lore.kernel.org/r/20200123131236.1078-2-sibis@codeaurora.org


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