Revert "usb: dwc2: gadget: change variable name to more meaningful"

This reverts commit ba48eab8 ("usb: dwc2: gadget: change variable
name to more meaningful").

This is needed to cleanly revert commit aa381a72 ("usb: dwc2:
gadget: fix TX FIFO size and address initialization") which may cause
regressions on some platforms.

Signed-off-by: John Youn <johnyoun@synopsys.com>
Cc: Robert Baldyga <r.baldyga@samsung.com>
Cc: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>