qede: Fix statistics' strings for Tx/Rx queues

When an interface is configured to use Tx/Rx-only queues,
the length of the statistics would be shortened to accomodate only the
statistics required per-each queue, and the values would be provided
accordingly.
However, the strings provided would still contain both Tx and Rx strings
for each one of the queues [regardless of its configuration], which might
lead to out-of-bound access when filling the buffers as well as incorrect
statistics presented.

Fixes: 9a4d7e86 ("qede: Add support for Tx/Rx-only queues.")
Signed-off-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>