f2fs: remove unneeded set_cold_node()

When setting COLD_BIT_SHIFT flag in node block, we only need to call
set_cold_node() in new_node_page() and recover_inode_page() during
node page initialization. So remove unneeded set_cold_node() in other
places.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>