block: export blk_{get,put}_queue()

BugLink: http://bugs.launchpad.net/bugs/802383

commit d86e0e83b32bc84600adb0b6ea1fce389b266682 upstream.

We need them in SCSI to fix a bug, but currently they are not
exported to modules. Export them.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>