usb: dwc3: of-simple: add support for the Amlogic Meson GXL and AXG SoCs

Amlogic Meson GXL and AXG SoCs come with a (host-only) dwc3 USB
controller. To use this controller a clock has to be enabled and a reset
line has to be pulsed.
Enabling the clock works identical to other SoCs. However, the reset
line has to be pulsed (using reset_control_reset) instead of using a
level reset (reset_control_{assert,deassert}).

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Tested-by: Yixun Lan <yixun.lan@amlogic.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>