f2fs: remove redundant goto statement in f2fs_read_single_page()

After the commit "0a4ee518", this "goto" statement was redundant,
remote it for clean code.

Signed-off-by: Li Zetao <lizetao1@huawei.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>