libext2fs: only use override function when reading an 128 byte inode

libext2fs: only use override function when reading an 128 byte inode

The ext2fs_read_inode_full() function should not use fs->read_inode()
if the caller has requested more than the base 128 byte inode
structure and the inode size is greater than 128 bytes.  Otherwise the
caller won't get all of the bytes that they were asking for, since
there's no way for the fs->read_inode override function can know what
the size of the buffer passed to ext2fs_read_inode_full().

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>