fs: Add initial atomic write support info to statx

fs: Add initial atomic write support info to statx

Extend statx system call to return additional info for atomic write support
support for a file.

Helper function generic_fill_statx_atomic_writes() can be used by FSes to
fill in the relevant statx fields. For now atomic_write_segments_max will
always be 1, otherwise some rules would need to be imposed on iovec length
and alignment, which we don't want now.

Signed-off-by: Prasad Singamsetty <[email protected]>
jpg: relocate bdev support to another patch
Reviewed-by: Darrick J. Wong <[email protected]>
Reviewed-by: Martin K. Petersen <[email protected]>
Signed-off-by: John Garry <[email protected]>
Acked-by: Darrick J. Wong <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>