f2fs: detect more inconsistent cases in sanity_check_node_footer()

f2fs: detect more inconsistent cases in sanity_check_node_footer()

Let's enhance sanity_check_node_footer() to detect more inconsistent
cases as below:

Node Type			Node Footer Info
===================		=============================
NODE_TYPE_REGULAR		inode = true and xnode = true
NODE_TYPE_INODE			inode = false or xnode = true
NODE_TYPE_XATTR			inode = true or xnode = false
NODE_TYPE_NON_INODE		inode = false

Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>