erofs-utils: lib: avoid exporting non-EROFS xattrs

Move all non-EROFS xattr macros to xattr.c and introduce
erofs_set_opaque_xattr() helper to hide all these details.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20230909163240.42057-3-hsiangkao@linux.alibaba.com
3 files changed