wifi: ath12k: move HE capabilities processing to a new function

The function ath12k_mac_copy_sband_iftype_data() is currently
used HE capabilities propagation but it can be extended to
include EHT data. Move the HE specific functionality from to
ath12k_mac_copy_he_cap() to make EHT additions easier.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.0.1-00029-QCAHKSWPL_SILICONZ-1
Signed-off-by: Aloka Dixit <quic_alokad@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230725224034.14045-3-quic_alokad@quicinc.com