mmc: sdhci: Auto-CMD23 fixes.

Fixes bugs in Auto-CMD23 feature enable decision. Auto-CMD23
should be enabled if host is >= v3, and SDMA is not in use.

USE_ADMA | USE_SDMA | Auto-CMD23
---------+----------+-----------
    0    |    0     |     1
---------+----------+-----------
    0    |    1     |     0
---------+----------+-----------
    1    |    0     |     1
---------+----------+-----------
    1    |    1     |     1

Signed-off-by: Andrei Warkentin <andreiw@motorola.com>
Signed-off-by: Chris Ball <cjb@laptop.org>