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: Christoph Hellwig <hch@lst.de>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20190903084615.19161-7-hch@lst.de


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>