fs/isofs/namei.c: Remove uninitialized local vars warning

shut up those:
fs/isofs/namei.c: In function 'isofs_lookup':
fs/isofs/namei.c:161: warning: 'offset' may be used uninitialized in this function
fs/isofs/namei.c:161: warning: 'block' may be used uninitialized in this function

By the way, they get overwritten at the end of isofs_find_entry().

Signed-off-by: Borislav Petkov <bbpetkov@yahoo.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>