phy: qcom-ufs: Use iopoll.h readl_poll_timeout macro

The private copy of readl_poll_timeout is no longer needed.
Use the implementation in iopoll.h instead.

Signed-off-by: Marc Gonzalez <marc.w.gonzalez@free.fr>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Andy Gross <andy.gross@linaro.org>
Reviewed-by: Vivek Gautam <vivek.gautam@codeaurora.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>