md: set md-specific flags for all queue limits

md: set md-specific flags for all queue limits

The md driver wants to enforce a number of flags to an all devices, even
when not inheriting them from the underlying devices.  To make sure these
flags survive the queue_limits_set calls that md uses to update the
queue limits without deriving them form the previous limits add a new
md_init_stacking_limits helper that calls blk_set_stacking_limits and sets
these flags.

Fixes: 1122c0c1cc71 ("block: move cache control settings out of queue->flags")
Signed-off-by: Christoph Hellwig <hch@lst.de>