Revert "Documentation: devicetree: dwc2: Deprecate g-tx-fifo-size"

Revert "Documentation: devicetree: dwc2: Deprecate g-tx-fifo-size"

This binding was deprecated due to commit cdf262e685a2 ("usb: dwc2:
gadget: fix TX FIFO size and address initialization"). However that
commit is now reverted, so also revert this commit.

The binding is valid and shouldn't be deprecated.

This reverts commit 780b952f83c8 ("Documentation: devicetree: dwc2:
Deprecate g-tx-fifo-size").

Signed-off-by: John Youn <johnyoun@synopsys.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>