CVE-2024-26632 block: Fix iterating over an empty bio with bio_for_each_folio_all

In the Linux kernel, the following vulnerability has been resolved:

block: Fix iterating over an empty bio with bio_for_each_folio_all

If the bio contains no data, bio_first_folio() calls page_folio() on a
NULL pointer and oopses. Move the test that we’ve reached the end of
the bio from bio_next_folio() to bio_first_folio().

[axboe: add unlikely() to error case]