iio: adc: TI_AM335X_ADC should depend on HAS_DMA

If NO_DMA=y:

    ERROR: "bad_dma_ops" [drivers/iio/adc/ti_am335x_adc.ko] undefined!

Add a dependency on HAS_DMA to fix this.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Fixes: f438b9da (" drivers: iio: ti_am335x_adc: add dma support")
Cc: <stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/adc/Kconfig

@@ -561,7 +561,7 @@ config TI_ADS8688
 
 config TI_AM335X_ADC
 	tristate "TI's AM335X ADC driver"
-	depends on MFD_TI_AM335X_TSCADC
+	depends on MFD_TI_AM335X_TSCADC && HAS_DMA
 	select IIO_BUFFER
 	select IIO_KFIFO_BUF
 	help