MLK-9699: ARM: dts: imx6: enable spi dma support

MLK-9699: ARM: dts: imx6: enable spi dma support

This patch cherry-pick from the below commit, but make little change:
align i.mx6dl with i.mx6q, since TKT238285 should be exit on other chips
although it can't reproduced by SPI-NOR, now there is official workaround
for this bug(a619a00e11a67b00805b9148f004a3c94d54f863). So this patch just
enable dma support on i.mx6sl and i.mx6sx.

*****************
There is one BUG(TKT238285) in ecspi module in DMA mode,but
it only found on i.mx6dl now, so enable dma support on all
i.mx6 chips except i.mx6dl

Signed-off-by: Robin Gong <b38343@freescale.com>
(cherry picked from commit fa9ef1796819aadbb1ea184613d4fdd3de1b46c6)
(cherry picked from commit cfedad0e853fbcd5e57591b559734d54cdb782c8)