spi: pxa2xx: Rewrite switch code block in interrupt_transfer

Rewrite switch code block to directly do the expected number
of shifts in each case and have break statements.

Addresses-Coverity-ID: 1056539 ("Missing break in switch")
Suggested-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-pxa2xx.c

@@ -665,9 +665,11 @@ static irqreturn_t interrupt_transfer(struct driver_data *drv_data)
 			bytes_left = drv_data->rx_end - drv_data->rx;
 			switch (drv_data->n_bytes) {
 			case 4:
-				bytes_left >>= 1;
+				bytes_left >>= 2;
+				break;
 			case 2:
 				bytes_left >>= 1;
+				break;
 			}
 
 			rx_thre = pxa2xx_spi_get_rx_default_thre(drv_data);