drivers: spi: mchp_mss: Handle NULL buffers better

At the moment, if you would pass a NULL buffer to the driver, the rx and
tx counts of that buffer would not advance. This patch fixes that.

Signed-off-by: Christian Mauderer <[email protected]>

Author: c-mauderer

drivers/spi/spi_mchp_mss.c

@@ -205,19 +205,19 @@ static inline void mss_spi_readwr_fifo(const struct device *dev)
 			rx_raw = mss_spi_read(cfg, MSS_SPI_REG_RX_DATA);
 			if (spi_context_rx_buf_on(ctx)) {
 				UNALIGNED_PUT(rx_raw, (uint8_t *)ctx->rx_buf);
-				spi_context_update_rx(ctx, 1, 1);
 			}
+			spi_context_update_rx(ctx, 1, 1);
 			++transfer_idx;
 		}
 
 		if (!(mss_spi_read(cfg, MSS_SPI_REG_STATUS) & MSS_SPI_STATUS_TXFIFO_FULL)) {
 			if (spi_context_tx_buf_on(ctx)) {
 				data8 = ctx->tx_buf[0];
 				mss_spi_write(cfg, MSS_SPI_REG_TX_DATA, data8);
-				spi_context_update_tx(ctx, 1, 1);
 			} else {
 				mss_spi_write(cfg, MSS_SPI_REG_TX_DATA, 0x0);
 			}
+			spi_context_update_tx(ctx, 1, 1);
 		}
 	}
 }