wifi: iwlwifi: Validate slots_num before allocating memory

Verify slots_num is valid in iwl_txq_alloc()

Signed-off-by: Anjaneyulu <pagadala.yesu.anjaneyulu@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230614123447.90be48017c1b.I880e451e137c5cd688d5f38b573b0dbf352762b3@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>