spi/xilinx: Use cached value of register

The control register has not changed since the previous access.
Therefore we can use the cached value and safe one bus access.
Signed-off-by: NRicardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: NMark Brown <broonie@kernel.org>

drivers/spi/spi-xilinx.c

@@ -271,7 +271,6 @@ static int xilinx_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
 		 * transmitter while the Isr refills the transmit register/FIFO,
 		 * or make sure it is stopped if we're done.
 		 */
-		cr = xspi->read_fn(xspi->regs + XSPI_CR_OFFSET);
 		xspi->write_fn(cr | XSPI_CR_TRANS_INHIBIT,
 			       xspi->regs + XSPI_CR_OFFSET);