The commit below added code to dump the content of FIFOs
that are present only on dual CPU products (8000 and up).
This broke 7265D whose firmware does advertise
IWL_UCODE_TLV_CAPA_EXTEND_SHARED_MEM_CFG but doesn't have 2
CPUs. The current code does check the length of the FIFO
before dumping them (and the nonexistent FIFO has a 0
length), but we still accessed a register to set the FIFO
number and that made the DMA unhappy.

The impact was a much longer recovery upon firmware assert.

Fixes: 5b086414 ("iwlwifi: mvm: support dumping UMAC internal txfifos")
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>