dt-bindings: usb: dwc3: Add DWC_usb3 TX/RX threshold configurable

In Synopsys's dwc3 data book:
To avoid underrun and overrun during the burst, in a high-latency bus
system (like USB), threshold and burst size control is provided through
GTXTHRCFG and GRXTHRCFG registers.
By default, USB TX and RX threshold are not enabled. To enable
TX or RX threshold, both packet threshold count and max burst size
properties must be set to a valid non-zero value.

In Realtek DHC SoC, DWC3 USB 3.0 uses AHB system bus. When dwc3 is
connected with USB 2.5G Ethernet, there will be overrun problem.
Therefore, setting TX/RX thresholds can avoid this issue.

Signed-off-by: Stanley Chang <stanley_chang@realtek.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230912041904.30721-2-stanley_chang@realtek.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>