f2fs: clean up f2fs_lookup
f2fs: clean up f2fs_lookup

This patch cleans up to avoid deep indentation.

Signed-off-by: Jaegeuk Kim <71255387a32c360dfbe6dfb7aaeb123bf1dc8cb6@kernel.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs