fat: fix parse_options()

Current parse_options() exits too early.  We need to run the code of
bottom in this function even if users doesn't specify options.

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>