btrfs_submit_compressed_read() is lack of memory allocation checks and
corresponding error route.

After this fix, if it comes to "no memory" case, errno will be returned
to userland step by step, and tell users this operation cannot go on.
Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>