spi: ep93xx: update kerneldoc comments for ep93xx_spi

Two fields got removed but are still documented:

drivers/spi/spi-ep93xx.c:98: warning: Excess struct member 'dma_rx_data' description in 'ep93xx_spi'
drivers/spi/spi-ep93xx.c:98: warning: Excess struct member 'dma_tx_data' description in 'ep93xx_spi'

Fixes: 3cfe73256905 ("spi: ep93xx: add DT support for Cirrus EP93xx")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/spi/spi-ep93xx.c

@@ -76,8 +76,6 @@
  *              frame decreases this level and sending one frame increases it.
  * @dma_rx: RX DMA channel
  * @dma_tx: TX DMA channel
- * @dma_rx_data: RX parameters passed to the DMA engine
- * @dma_tx_data: TX parameters passed to the DMA engine
  * @rx_sgt: sg table for RX transfers
  * @tx_sgt: sg table for TX transfers
  * @zeropage: dummy page used as RX buffer when only TX buffer is passed in by