net: intel: fm10k: Fix parameter idx set but not used

Variable idx is set in the loop, but is never used resulting in dead
code. Building with GCC 16, which enables
-Werror=unused-but-set-parameter= by default results in build error.
This patch removes the idx parameter, since all the callers of the
fm10k_unbind_hw_stats_q as 0 as idx anyways.

Suggested-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Signed-off-by: Brahmajit Das <listout@listout.xyz>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>