ibmvnic: Rename active queue count variables

Rename the tx/rx active pool variables to be tx/rx active scrq
counts. The tx/rx pools are per sub-crq so this is a more appropriate
name. This also is a preparatory step for using thiese variables
for handling updates to sub-crqs and napi based on the active
count.

Signed-off-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>