usb: dwc2: replace ioread32/iowrite32_rep with dwc2_readl/writel_rep

dwc2_readl_rep/dwc2_writel_rep functions using readl/writel in a
loop.

Signed-off-by: Gevorg Sahakyan <sahakyan@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>