wifi: iwlwifi: tests: allow same config for different MACs

For different MACs we maintain the configs in different
files, and while it's a small waste of space, this is a
worthwhile trade-off for maintenance and simplicity. So
allow different MAC types to have the same config. This
could allow the same config for two MACs in the same MAC
family, but that's not hugely important. Also simplify
the test to not build a config list, there's no good
reason to do that.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250504132447.27f5d570eb32.I1649309a0e54a1d446a38c5b2124a582de9f6d61@changeid