wifi: mt76: mt7915: fix double hif2 init on the non-WED path

In the Linux kernel, the following vulnerability has been resolved: wifi: mt76: mt7915: fix double hif2 init on the non-WED path mt7915_pci_init_hif2() was called unconditionally and again inside the WED-inactive branch. The helper increments the global hif_idx, writes the PCIe RECOG_ID register and takes a get_device() reference via mt7915_pci_get_hif2(), while removal only drops one reference. On non-WED dual-hif hardware this double-incremented hif_idx, wrote RECOG_ID twice and leaked a device reference. Only the call inside the WED-inactive branch is correct; drop the unconditional one. hif2 is already initialised to NULL.