wifi: iwlwifi: pcie move gen1_2 probe to gen1_2/trans.c

In the process of splitting the transport's different generations,
move gen1_2's probe flow and relevant helper functions to the gen1_2
subfolder

Signed-off-by: Yedidya Benshimol <yedidya.ben.shimol@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250709081300.29b909144e1a.Idaa77eddd6650cf6f113833d2fbc8d3ef08cfd8f@changeid