split hard read-only vs read-only policy v2

[Christoph Hellwig]

Hi Jens,

this series resurrects a patch from Martin to properly split the flag
indicating a disk has been set read-only by the hardware vs the userspace
policy set through the BLKROSET ioctl.

This series is based on top of the

   "merge struct block_device and struct hd_struct v4"

series and won't apply to mainline or Jens' for-5.11 tree.

A git tree is available here:

    git://git.infradead.org/users/hch/block.git block-hard-ro

Gitweb:

    http://git.infradead.org/users/hch/block.git/shortlog/refs/heads/block-hard-ro


Changes since v1:
 - don't propagate the policy flag from the whole disk to partitions
 - rebased on top of the merge block_device and hd_struct series