vfs_fruit: Fix CID 1433613 Operands don't affect result

vfs_fruit: Fix CID 1433613 Operands don't affect result

Two changes: First, we can't check multiplication overflow after the
operation. This has to be done before with a division. Second, there
is no OFF_T_MAX, and both operands are size_t, so check for
SIZE_MAX. The result is assigned to off_t, but I'm not sure where the
automatic coercion from size_t to off_t would happen.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>