libext2fs: don't fail when doing a strict rewrite of inline data

libext2fs: don't fail when doing a strict rewrite of inline data

ext2fs_inline_data_set() tries to ensure that there is sufficient free
space in the inode to store the inline data.  Unfortunately, it gets
the check wrong -- ext2fs_xattr_inode_max_size() returns the amount of
unused bytes in the EA area, and _data_set() doesn't factor in the
size of the existing inline data.  Therefore, a strict rewrite of an
N-byte inlinedata with another N-byte inlinedata fails.

Fix the code to do the size check correctly.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>