iwlwifi: mvm: fix a range check in debugfs code

The &mvm->tof_data.range_req.ap[] array has IWL_MVM_TOF_MAX_APS elements
so the check should be >= instead of >.  Also the test can underflow so
I have changed "i" to unsigned.

Fixes: ce792918 ('wlwifi: mvm: add basic Time of Flight (802.11mc FTM) support')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>