dt-bindings: dma: drop unneeded quotes

Cleanup by removing unneeded quotes from refs and redundant blank lines.
No functional impact except adjusting to preferred coding style.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com> # mediatek
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Hector Martin <marcan@marcan.st> # apple
Acked-by: Paul Cercueil <paul@crapouillou.net>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org> # Spear
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com> # Renesas
Reviewed-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com> # Socionext
Link: https://lore.kernel.org/r/20230124081117.31186-1-krzysztof.kozlowski@linaro.org


Signed-off-by: Vinod Koul <vkoul@kernel.org>