usb:cdnsp: remove TRB_FLUSH_ENDPOINT command

Patch removes TRB_FLUSH_ENDPOINT command from driver.
This command is not supported by controller and
USBSSP returns TRB Error completion code for it.

Signed-off-by: Pawel Laszczak <pawell@cadence.com>
Acked-by: Peter Chen <peter.chen@kernel.org>
Link: https://lore.kernel.org/r/20231026073737.165450-1-pawell@cadence.com


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