Blackfin serial driver Kconfig: depend on DMA not being enabled rather than a specific DMA size

Signed-off-by: Mike Frysinger <michael.frysinger@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 87665d7d..ed438bc 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -624,7 +624,7 @@
 
 config SERIAL_BFIN_DMA
 	bool "DMA mode"
-	depends on DMA_UNCACHED_1M && !KGDB_UART
+	depends on !DMA_UNCACHED_NONE && !KGDB_UART
 	help
 	  This driver works under DMA mode. If this option is selected, the
 	  blackfin simple dma driver is also enabled.