wifi: brcmfmac: avoid invalid list operation when vendor attach fails

When the brcmf_fwvid_attach() fails the driver instance is not added
to the vendor list. Hence we should not try to delete it from that
list when the brcmf_fwvid_detach() function is called in cleanup path.

Cc: stable@vger.kernel.org # 6.2.x
Fixes: d6a5c562 ("wifi: brcmfmac: add support for vendor-specific firmware api")
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240106103835.269149-3-arend.vanspriel@broadcom.com