staging: et131x: Reduce split lines by renaming some psr variables

Modify some packet status ring associated variables to save a few
split lines:

pktstat_ringsize -> psr_size
psr_num_entries -> psr_entries
index -> ii

Signed-off-by: Mark Einon <mark.einon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>