ath11k: wmi: put hardware to DBS mode

For QCA6390, host puts hardware to Dual Band Simultaneous (DBS) mode by default
so both 2G and 5G bands can be used. Otherwise only the 5G band can be used.
QCA6390 doesn't provide band_to_mac configuration and firmware will do the
band_to_mac map.

Tested-on: QCA6390 hw2.0 PCI WLAN.HST.1.0.1-01740-QCAHSTSWPLZ_V2_TO_X86-1
Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.1.0.1-01238-QCAHKSWPL_SILICONZ-2

Signed-off-by: Carl Huang <cjhuang@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1597576599-8857-12-git-send-email-kvalo@codeaurora.org