md/raid1: don't set array_frozen in raid1_takeover()

In the Linux kernel, the following vulnerability has been resolved: md/raid1: don't set array_frozen in raid1_takeover() raid1_takeover() sets conf->array_frozen = 1 on the newly-allocated r1conf and nothing ever clears it, so every I/O to the array stalls permanently once _wait_barrier() sees it stuck at 1. This used to be harmless: level_store() called mddev_resume() right after pers->run(), which called raid1_quiesce(mddev, 0) and cleared array_frozen back to 0 regardless of what raid1_takeover() set. Commit b39f35ebe86d ("md: don't quiesce in mddev_suspend()") removed that quiesce(mddev, 0) call, so the pre-set now sticks. setup_conf() already zero-initializes the new r1conf via kzalloc, so just don't set array_frozen here. Same class of bug as commit 892da88d1cd9 ("md/raid10: fix a 'conf->barrier' leakage in raid10_takeover()"), also triggered by b39f35ebe86d.