dwmmc: Increase retry timeout

When enable dcache on HiKey, we're running into MMC command timeouts
because our retry loop is now faster than the eMMC (or an external SD
card) can answer.

Increase the retry count to the same as the timeout value for status
reports.

The real fix is obviously to not base this whole thing on a cycle counter
but on real wall time, but that would be slightly more intrusive.

Signed-off-by: Alexander Graf <agraf@suse.de>