iwlwifi: fix warnings produced by kernel debug options

Fix warnings produced by:
- lockdep_assert_wiphy() in function reg_process_self_managed_hint(),
- wiphy_dereference() in function iwl_mvm_init_fw_regd().
Both function are expected to be called in critical section.

The warnings were discovered when running v5.15 kernel
with debug options enabled:

1)
Hardware name: Google Delbin/Delbin
RIP: 0010:reg_process_self_managed_hint+0x254/0x347 [cfg80211]
...
Call Trace:
regulatory_set_wiphy_regd_sync+0x3d/0xb0
iwl_mvm_init_mcc+0x49d/0x5a2
iwl_op_mode_mvm_start+0x1b58/0x2507
? iwl_mvm_reprobe_wk+0x94/0x94
_iwl_op_mode_start+0x146/0x1a3
iwl_opmode_register+0xda/0x13d
init_module+0x28/0x1000

2)
drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c:263 suspicious rcu_dereference_protected() usage!
...
Hardware name: Google Delbin/Delbin, BIOS Google_Delbin
Call Trace:
dump_stack_lvl+0xb1/0xe6
iwl_mvm_init_fw_regd+0x2e7/0x379
iwl_mvm_init_mcc+0x2c6/0x5a2
iwl_op_mode_mvm_start+0x1b58/0x2507
? iwl_mvm_reprobe_wk+0x94/0x94
_iwl_op_mode_start+0x146/0x1a3
iwl_opmode_register+0xda/0x13d
init_module+0x28/0x100

Fixes: a05829a7 ("cfg80211: avoid holding the RTNL when calling the driver")
Signed-off-by: Łukasz Bartosik <lb@semihalf.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20211110215744.5487-1-lukasz.bartosik@semihalf.com

drivers/net/wireless/intel/iwlwifi/mvm/ops.c

@@ -686,6 +686,7 @@ static int iwl_mvm_start_get_nvm(struct iwl_mvm *mvm)
 	int ret;
 
 	rtnl_lock();
+	wiphy_lock(mvm->hw->wiphy);
 	mutex_lock(&mvm->mutex);
 
 	ret = iwl_run_init_mvm_ucode(mvm);
@@ -701,6 +702,7 @@ static int iwl_mvm_start_get_nvm(struct iwl_mvm *mvm)
 		iwl_mvm_stop_device(mvm);
 
 	mutex_unlock(&mvm->mutex);
+	wiphy_unlock(mvm->hw->wiphy);
 	rtnl_unlock();
 
 	if (ret < 0)