f2fs: set sb->s_fs_info before calling parse_options()

In f2fs_fill_super(), set sb->s_fs_info before calling parse_options(), then we can get
f2fs_sb_info via F2FS_SB(sb) in parse_options().
So that the second argument "sbi" of func parse_options() is no longer needed.

Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>