spi: npcm-fiu: Fix UMA reads when dummy.nbytes == 0

We don't want to use the value of ilog2(0) as dummy.buswidth is 0 when
dummy.nbytes is 0. Since we have no dummy bytes, we don't need to
configure the dummy byte bits per clock register value anyway.
Signed-off-by: "William A. Kennington III" <william@wkennington.com>
Link: https://lore.kernel.org/r/20230922182812.2728066-1-william@wkennington.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-npcm-fiu.c

@@ -353,8 +353,9 @@ static int npcm_fiu_uma_read(struct spi_mem *mem,
 		uma_cfg |= ilog2(op->cmd.buswidth);
 		uma_cfg |= ilog2(op->addr.buswidth)
 			<< NPCM_FIU_UMA_CFG_ADBPCK_SHIFT;
-		uma_cfg |= ilog2(op->dummy.buswidth)
-			<< NPCM_FIU_UMA_CFG_DBPCK_SHIFT;
+		if (op->dummy.nbytes)
+			uma_cfg |= ilog2(op->dummy.buswidth)
+				<< NPCM_FIU_UMA_CFG_DBPCK_SHIFT;
 		uma_cfg |= ilog2(op->data.buswidth)
 			<< NPCM_FIU_UMA_CFG_RDBPCK_SHIFT;
 		uma_cfg |= op->dummy.nbytes << NPCM_FIU_UMA_CFG_DBSIZ_SHIFT;