mfd: don't select DMA_DECLARE_COHERENT for the sm501 and tc6393xb drivers

Now that these drivers use the usb localmem pool there is no need to
select DMA_DECLARE_COHERENT.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Tested-by: NGuenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20190903084615.19161-7-hch@lst.deSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/mfd/Kconfig

@@ -1105,7 +1105,6 @@ config MFD_SI476X_CORE
 config MFD_SM501
 	tristate "Silicon Motion SM501"
 	depends on HAS_DMA
-	select DMA_DECLARE_COHERENT
 	 ---help---
 	  This is the core driver for the Silicon Motion SM501 multimedia
 	  companion chip. This device is a multifunction device which may
@@ -1714,7 +1713,6 @@ config MFD_TC6393XB
 	select GPIOLIB
 	select MFD_CORE
 	select MFD_TMIO
-	select DMA_DECLARE_COHERENT
 	help
 	  Support for Toshiba Mobile IO Controller TC6393XB