usb: dwc3: Add Amlogic G12A DWC3 glue

Adds support for Amlogic G12A USB Control Glue HW.

The Amlogic G12A SoC Family embeds 2 USB Controllers :
- a DWC3 IP configured as Host for USB2 and USB3
- a DWC2 IP configured as Peripheral USB2 Only

A glue connects these both controllers to 2 USB2 PHYs, and optionnally
to an USB3+PCIE Combo PHY shared with the PCIE controller.

The Glue configures the UTMI 8bit interfaces for the USB2 PHYs, including
routing of the OTG PHY between the DWC3 and DWC2 controllers, and
setups the on-chip OTG mode selection for this PHY.

This drivers supports the on-probe setup of the OTG mode, and manually
via a debugfs interface. The IRQ mode change detect is yet to be added
in a future patchset, mainly due to lack of hardware to validate on.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/Kconfig

@@ -96,6 +96,16 @@ config USB_DWC3_KEYSTONE
 	  Support of USB2/3 functionality in TI Keystone2 and AM654 platforms.
 	  Say 'Y' or 'M' here if you have one such device
 
+config USB_DWC3_MESON_G12A
+       tristate "Amlogic Meson G12A Platforms"
+       depends on OF && COMMON_CLK
+       depends on ARCH_MESON || COMPILE_TEST
+       default USB_DWC3
+       select USB_ROLE_SWITCH
+       help
+         Support USB2/3 functionality in Amlogic G12A platforms.
+	 Say 'Y' or 'M' if you have one such device.
+
 config USB_DWC3_OF_SIMPLE
        tristate "Generic OF Simple Glue Layer"
        depends on OF && COMMON_CLK