f2fs: Clean up the loop outside of f2fs_invalidate_blocks()

Now f2fs_invalidate_blocks() supports a continuous range of addresses,
so the for loop can be omitted.

Signed-off-by: Yi Sun <yi.sun@unisoc.com>
Signed-off-by: Zhiguo Niu <zhiguo.niu@unisoc.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>