dm-unstriped: cast an operand to sector_t to prevent potential uint32_t overflow

dm-unstriped: cast an operand to sector_t to prevent potential uint32_t overflow

This was found by a static analyzer.
There may be a potential integer overflow issue in
unstripe_ctr(). uc->unstripe_offset and uc->unstripe_width are
defined as "sector_t"(uint64_t), while uc->unstripe,
uc->chunk_size and uc->stripes are all defined as "uint32_t".
The result of the calculation will be limited to "uint32_t"
without correct casting.
So, we recommend adding an extra cast to prevent potential
integer overflow.

Fixes: 18a5bf270532 ("dm: add unstriped target")
Signed-off-by: Zichen Xie <zichenxie0106@gmail.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org