serial: SERIAL_MXS_AUART should depend on HAS_DMA

If NO_DMA=y:

    ERROR: "dma_unmap_sg" [drivers/tty/serial/mxs-auart.ko] undefined!
    ERROR: "dma_map_sg" [drivers/tty/serial/mxs-auart.ko] undefined!

Add a dependency on HAS_DMA to fix this.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/Kconfig

@@ -1411,8 +1411,9 @@ config SERIAL_PCH_UART_CONSOLE
 	  warnings and which allows logins in single user mode).
 
 config SERIAL_MXS_AUART
-	depends on ARCH_MXS || COMPILE_TEST
 	tristate "MXS AUART support"
+	depends on HAS_DMA
+	depends on ARCH_MXS || COMPILE_TEST
 	select SERIAL_CORE
 	select SERIAL_MCTRL_GPIO if GPIOLIB
 	help