f2fs: add a f2fs_ prefix to punch_hole() and expand_inode_data()

For example, f2fs_collapse_range(), f2fs_collapse_range(),
f2fs_insert_range(), the functions used in f2fs_fallocate()
are all prefixed with f2fs_, so let's keep the name consistent.

Signed-off-by: Yangtao Li <frank.li@vivo.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>