ath11k: Change number of TCL rings to one for QCA6390

Some targets, QCA6390 for example, use only one TCL ring, it is better to
initialize only one ring and leave others untouched for such targets.

This is a theoretical fix found during code review, no visible impact.

Tested-on: QCA6390 hw2.0 PCI WLAN.HST.1.0.1-01740-QCAHSTSWPLZ_V2_TO_X86-1

Signed-off-by: Baochen Qiang <bqiang@codeaurora.org>
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210914163726.38604-1-jouni@codeaurora.org