spi: fsl-lpspi: remove unneeded array

- replace the array with the shift operation
- remove the extra comparing operation.
Signed-off-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
Link: https://lore.kernel.org/r/20200220141143.3902922-2-oleksandr.suvorov@toradex.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-fsl-lpspi.c

@@ -86,8 +86,6 @@
 #define TCR_RXMSK	BIT(19)
 #define TCR_TXMSK	BIT(18)
 
-static int clkdivs[] = {1, 2, 4, 8, 16, 32, 64, 128};
-
 struct lpspi_config {
 	u8 bpw;
 	u8 chip_select;
@@ -331,15 +329,14 @@ static int fsl_lpspi_set_bitrate(struct fsl_lpspi_data *fsl_lpspi)
 	}
 
 	for (prescale = 0; prescale < 8; prescale++) {
-		scldiv = perclk_rate /
-			 (clkdivs[prescale] * config.speed_hz) - 2;
+		scldiv = perclk_rate / config.speed_hz / (1 << prescale) - 2;
 		if (scldiv < 256) {
 			fsl_lpspi->config.prescale = prescale;
 			break;
 		}
 	}
 
-	if (prescale == 8 && scldiv >= 256)
+	if (scldiv >= 256)
 		return -EINVAL;
 
 	writel(scldiv | (scldiv << 8) | ((scldiv >> 1) << 16),