block: Eliminate DriveInfo member bdrv, use blk_by_legacy_dinfo()

block: Eliminate DriveInfo member bdrv, use blk_by_legacy_dinfo()

The patch is big, but all it really does is replacing

    dinfo->bdrv

by

    blk_bs(blk_by_legacy_dinfo(dinfo))

The replacement is repetitive, but the conversion of device models to
BlockBackend is imminent, and will shorten it to just
blk_legacy_dinfo(dinfo).

Line wrapping muddies the waters a bit.  I also omit tests whether
dinfo->bdrv is null, because it never is.

Signed-off-by: Markus Armbruster <[email protected]>
Reviewed-by: Benoît Canet <[email protected]>
Reviewed-by: Max Reitz <[email protected]>
Reviewed-by: Kevin Wolf <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>