erofs-utils: fix multiple definition of `sbi'

As nl6720 reported [1], lib/inode.o (mkfs) and lib/super.o (erofsfuse)
could be compiled together by some options. Fix it now.

[1] https://lore.kernel.org/r/10789285.Na0ui7I3VY@walnut

Link: https://lore.kernel.org/r/20201208105741.9614-1-hsiangkao@aol.com
Fixes: 5e35b75ad499 ("erofs-utils: introduce fuse implementation")
Reported-by: nl6720 <nl6720@gmail.com>
Reviewed-by: Li Guifu <bluce.lee@aliyun.com>
Signed-off-by: Gao Xiang <hsiangkao@aol.com>
3 files changed