ena: Fix LLQ descriptor reconfiguration

After the device reset, the LLQ configuration descriptor wasn't passed
to the hardware. On a 6-generation AWS instances (like C6gn), it is
required to pass the LLQ descriptor after the device reset, otherwise
the hardware will be missing the LLQ configuration resulting in
performance degradation.

This patch reconfigures the LLQ each time the ena_device_init() is
called. This means that the LLQ descriptor will be passed during the
initial configuration and after a reset.

The ena_map_llq_mem_bar() function call was moved before the
ena_device_init() call, to make sure that the mem bar is available.

Obtained from: Semihalf
MFC after: 2 weeks
Sponsored by: Amazon, Inc.