iomap: convert to SPDX identifier

Use SPDX-License-Identifier instead of GPLv2 boilerplate.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
1 file changed