spi: dw: Move dw_spi_can_dma()

Move dw_spi_can_dma() implementation below dw_spi_dma_convert_width()
for handing compile dependency in future patches.

* tested on Baikal-T1 based system with DW SPI-looped back interface
transferring a chunk of data with DFS:8,12,16.

Signed-off-by: Joy Chakraborty <joychakr@google.com
Reviewed-by: Serge Semin <fancer.lancer@gmail.com
Tested-by: Serge Semin <fancer.lancer@gmail.com
Link: https://lore.kernel.org/r/20230427123314.1997152-3-joychakr@google.com
Signed-off-by: Mark Brown <broonie@kernel.org

drivers/spi/spi-dw-dma.c

@@ -198,14 +198,6 @@ static irqreturn_t dw_spi_dma_transfer_handler(struct dw_spi *dws)
 	return IRQ_HANDLED;
 }
 
-static bool dw_spi_can_dma(struct spi_controller *master,
-			   struct spi_device *spi, struct spi_transfer *xfer)
-{
-	struct dw_spi *dws = spi_controller_get_devdata(master);
-
-	return xfer->len > dws->fifo_len;
-}
-
 static enum dma_slave_buswidth dw_spi_dma_convert_width(u8 n_bytes)
 {
 	switch (n_bytes) {
@@ -220,6 +212,14 @@ static enum dma_slave_buswidth dw_spi_dma_convert_width(u8 n_bytes)
 	}
 }
 
+static bool dw_spi_can_dma(struct spi_controller *master,
+			   struct spi_device *spi, struct spi_transfer *xfer)
+{
+	struct dw_spi *dws = spi_controller_get_devdata(master);
+
+	return xfer->len > dws->fifo_len;
+}
+
 static int dw_spi_dma_wait(struct dw_spi *dws, unsigned int len, u32 speed)
 {
 	unsigned long long ms;