block: Fix 32 bit truncation in mark_request_serialising()

block: Fix 32 bit truncation in mark_request_serialising()

On 32 bit hosts, size_t is too small for align as the bitmask
~(align - 1) will zero out the higher 32 bits of the offset.

While at it, change the local overlap_bytes variable to unsigned to
match the field in BdrvTrackedRequest.

Signed-off-by: Kevin Wolf <[email protected]>
Reviewed-by: Laszlo Ersek <[email protected]>