ARM: ux500: add some DB8500 DMA channel info

This adds some missing DMA channel information to the disabled
MMC/SD/SDIO blocks number 3 and 5, and notes that the assignment
of MSP channels vary with ASIC variant.

Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>