btrfs: cleanup device states define BTRFS_DEV_STATE_WRITEABLE

Currently device state is being managed by each individual int
variable such as struct btrfs_device::writeable. Instead of that
declare device state BTRFS_DEV_STATE_WRITEABLE and use the
bit operations.

Signed-off-by: Anand Jain <[email protected]>
[ whitespace adjustments ]
Signed-off-by: David Sterba <[email protected]>
7 files changed