usb: gadget: fusb300_udc: add FUSB300_EPSET0_STL_CLR for clearing EP0 stall

The final version of fusb300 controller adds EPSET0_STL_CLR
for clearing EP0 stall and also removes EPSET0_EPn_TX0BYTE.

fusb300_udc driver is tested on FARADAY platform a369 with
FUSB300 FPGA v1.8

Signed-off-by: Yuan-Hsin Chen <yhchen@faraday-tech.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>