Enable SGDMA support for SD_IO_RW_EXTENDED and add proper check
for scatterlist size alignment in block mode.

According to documentation, in SDIO block mode meson-gx DMA could
only handle buffers with sizes that are multiples of SDIO block size.

Some SDIO drivers like brcmfmac use scatterlist API, but do not enforce
proper scatterlist buffer size alignemnt, this looks like a root cause
of non-working CMD53.

Some minor style fixes.
Signed-off-by: Dmitry Lebed <lebed.dmitry@gmail.com>
Reviewed-by: Jerome Brunet <jbrunet@baylibre.com>
Link: https://lore.kernel.org/r/20201218075312.67338-1-lebed.dmitry@gmail.comSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>