rtlwifi: rtl_pci_probe: Fix fail path of _rtl_pci_find_adapter

_rtl_pci_find_adapter fail path will jump to label fail3 for
unsupported adapter types.

However, on course for fail3 there will be call rtl_deinit_core
before rtl_init_core.

For the inclusion of checking pci_iounmap this fail can be moved to
fail2.

Fixes
[    4.492963] BUG: unable to handle kernel NULL pointer dereference at           (null)
[    4.493067] IP: rtl_deinit_core+0x31/0x90 [rtlwifi]

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>