serial: SERIAL_STM32 should depend on HAS_DMA

If NO_DMA=y:

    drivers/built-in.o: In function `stm32_serial_remove':
    stm32-usart.c:(.text+0xcea1a): undefined reference to `bad_dma_ops'
    stm32-usart.c:(.text+0xcea7a): undefined reference to `bad_dma_ops'

Add a dependency on HAS_DMA to fix this.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/Kconfig

@@ -1625,6 +1625,7 @@ config SERIAL_SPRD_CONSOLE
 config SERIAL_STM32
 	tristate "STMicroelectronics STM32 serial port support"
 	select SERIAL_CORE
+	depends on HAS_DMA
 	depends on ARM || COMPILE_TEST
 	help
 	  This driver is for the on-chip Serial Controller on