wifi: iwlwifi: fix the ECKV UEFI variable name

This UEFI variable name was badly named. Fix its name and also use the
right GUID to find it: we need to use the BT_WIFI (a.k.a. Common) GUID.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250308231426.78c998d0fa71.I2bc9d72c1dc2c4d7028f0265634a940c2fadbbb5@changeid


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