spi: davinci: fix up dma_mapping_error() incorrect patch

spi: davinci: fix up dma_mapping_error() incorrect patch

commit aabb797b4c1204b2e8518538b2616e476f2bac92, which is commit
c5a2a394835f473ae23931eda5066d3771d7b2f8 upstream had an error in it.

Ben writes:
	The '!' needs to be deleted.  This appears to have been fixed upstream
	by:

	commit 8aedbf580d21121d2a032e4c8ea12d8d2d85e275
	Author: Fabien Parent <fparent@baylibre.com>
	Date:   Thu Feb 23 19:01:56 2017 +0100

	    spi: davinci: Use SPI framework to handle DMA mapping

	which is not suitable for stable.

So I'm just fixing this up directly.

Reported-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>