CVE-2026-46023: dm mirror: fix integer overflow in create_dirty_log()

In the Linux kernel, the following vulnerability has been resolved: dm mirror: fix integer overflow in create_dirty_log() The argument count calculation in create_dirty_log() performs `*args_used = 2 + param_count` before validating against argc. When a user provides a param_count close to UINT_MAX via the device mapper table string, this unsigned addition wraps around to a small value, causing the subsequent `argc < *args_used` check to be bypassed. The overflowed param_count is then passed as argc to dm_dirty_log_create(), where it can cause out-of-bounds reads on the argv array. Fix by comparing param_count against argc - 2 before performing the addition, following the same pattern used by parse_features() in the same file. Since argc >= 2 is already guaranteed, the subtraction is safe.