usb: dwc2: Use platform endianness when accessing registers

This patch switches calls to readl/writel to their
dwc2_readl/dwc2_writel equivalents which preserve platform endianness.

This patch is necessary to access dwc2 registers correctly on big-endian
systems such as the mips based SoCs made by Lantiq. Then dwc2 can be
used to replace ifx-hcd driver for Lantiq platforms found e.g. in
OpenWrt.

The patch was autogenerated with the following commands:
$EDITOR core.h
sed -i "s/\<readl\>/dwc2_readl/g" *.c hcd.h hw.h
sed -i "s/\<writel\>/dwc2_writel/g" *.c hcd.h hw.h

Some files were then hand-edited to fix checkpatch.pl warnings about
too long lines.

Signed-off-by: Antti Seppälä <a.seppala@gmail.com>
Signed-off-by: Vincent Pelletier <plr.vincent@gmail.com>
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>