wifi: iwlwifi: remove Gl A-step remnants

The IWL_DEVICE_GL_A macro is no longer used, and couldn't
be, so remove it.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Gregory Greenman <gregory.greenman@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20240129211905.8929a06c3a55.I3c21305e4b7fa3aba938bc860269e848fe262e88@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>