wifi: ath12k: ath12k_mac_op_set_key(): fix uninitialized symbol 'ret'

Dan reported that in some cases the ret variable could be uninitialized. Fix
that by removing the out label entirely and returning zero explicitly on
succesful cases.

Also remove the unnecessary else branches to follow more the style used in
ath12k and now it's easier to see the error handling.

No functional changes.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.3.1-00173-QCAHKSWPL_SILICONZ-1
Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/all/7e7afd00-ad84-4744-8d94-416bab7e7dd9@stanley.mountain/


Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://patch.msgid.link/20241126171139.2350704-10-kvalo@kernel.org