ath11k: don't initialize rxdma1 related ring

For QCA6390, it has 2 lmacs and thus 2 rxdmas. However, each rxdma has rxdma0
only, and doesn't have rxdma1. So for QCA6390, don't initialize rxdma1 related
rings such as rx_mon_buf_ring, rx_mon_dst_ring and rx_mon_desc_ring.

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/1597555891-26112-3-git-send-email-kvalo@codeaurora.org