wifi: iwlwifi: mvm: add mvm-specific guard

Add and use an mvm-specific guard for the mvm mutex.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20240512152312.7391425b3af2.I1b109f56753dd3f35602dd2c5cf6e1e35aee313d@changeid


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