hw/usb: Add basic i.MX USB Phy support

Add basic USB PHY support as implemented in i.MX23, i.MX28, i.MX6,
and i.MX7 SoCs.

The only support really needed - at least to boot Linux - is support
for soft reset, which needs to reset various registers to their initial
value. Otherwise, just record register values.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Message-id: 20200313014551.12554-2-linux@roeck-us.net
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index 32867bc..f8741ca 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -764,6 +764,8 @@
 F: hw/arm/fsl-imx6.c
 F: hw/misc/imx6_*.c
 F: hw/ssi/imx_spi.c
+F: hw/usb/imx-usb-phy.c
+F: include/hw/usb/imx-usb-phy.h
 F: include/hw/arm/fsl-imx6.h
 F: include/hw/misc/imx6_*.h
 F: include/hw/ssi/imx_spi.h