wifi: iwlwifi: mvm: don't try to talk to a dead firmware

wifi: iwlwifi: mvm: don't try to talk to a dead firmware

This fixes:

 bad state = 0
 WARNING: CPU: 10 PID: 702 at drivers/net/wireless/inel/iwlwifi/iwl-trans.c:178 iwl_trans_send_cmd+0xba/0xe0 [iwlwifi]
 Call Trace:
  <TASK>
  ? __warn+0xca/0x1c0
  ? iwl_trans_send_cmd+0xba/0xe0 [iwlwifi 64fa9ad799a0e0d2ba53d4af93a53ad9a531f8d4]
  iwl_fw_dbg_clear_monitor_buf+0xd7/0x110 [iwlwifi 64fa9ad799a0e0d2ba53d4af93a53ad9a531f8d4]
  _iwl_dbgfs_fw_dbg_clear_write+0xe2/0x120 [iwlmvm 0e8adb18cea92d2c341766bcc10b18699290068a]

Ask whether the firmware is alive before sending a command.

Fixes: 268712dc3b34 ("wifi: iwlwifi: mvm: add a debugfs hook to clear the monitor data")
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250209143303.8e1597b62c70.I12ea71dd9b805b095c9fc12a10c9f34a4e801b61@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>