ath10k: Drop WARN_ON()s that always trigger during system resume

ath10k_mac_vif_chan() always returns an error for the given vif
during system-wide resume which reliably triggers two WARN_ON()s
in ath10k_bss_info_changed() and they are not particularly
useful in that code path, so drop them.

Tested: QCA6174 hw3.2 PCI with WLAN.RM.2.0-00180-QCARMSWPZ-1
Tested: QCA6174 hw3.2 SDIO with WLAN.RMH.4.4.1-00007-QCARMSWP-1

Fixes: cd93b83a ("ath10k: support for multicast rate control")
Fixes: f279294e ("ath10k: add support for configuring management packet rate")
Cc: stable@vger.kernel.org
Reviewed-by: Brian Norris <briannorris@chromium.org>
Tested-by: Brian Norris <briannorris@chromium.org>
Tested-by: Claire Chang <tientzu@chromium.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>