btrfs: return a btrfs_inode from read_one_inode()

[ Upstream commit b4c50cbb ]

All callers of read_one_inode() are mostly interested in the btrfs_inode
structure rather than the VFS inode, so make read_one_inode() return
the btrfs_inode instead, avoiding lots of BTRFS_I() calls.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Stable-dep-of: 5f61b961 ("btrfs: fix inode lookup error handling during log replay")
Signed-off-by: Sasha Levin <sashal@kernel.org>