usb: dwc3: Revert Add support for nominal elastic buffer

Commit 3bb69751 ("usb: dwc3: Add support for nominal
elastic buffer") breaks working of current 5.4 kernel
based targets by clearing elastic buffer which is not
expected. Hence revert the change.

Change-Id: I3a492289eea1cb728c2e16ea1b991862d2219bbe
Signed-off-by: Rohith Kollalsi <rkollals@codeaurora.org>