iwlwifi: msix: limit max RX queues for 9000 family

There is an issue in the HW DMA engine in the 9000 family of devices
when more than 6 RX queues are used.  The issue is that the FW may
hang when IWL_MVM_RXQ_NSSN_SYNC notifications are sent.

Fix this by limiting the number of RX queues to 6 in the 9000 family
of devices.

Signed-off-by: Mordechay Goodstein <mordechay.goodstein@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200911204056.37d90f9ceb0c.I8dfe8a7d3a7ac9f0bc9d93e4a03f8165d8c999d2@changeid


Signed-off-by: Luca Coelho <luciano.coelho@intel.com>