systemc: Make the verify.py --list option print a total count.
systemc: Make the verify.py --list option print a total count.

Make the --list option of verify.py print a count of how many tests it
printed. Because --list respects the filter options, this is an easy
way to check how many tests have certain properties.

Change-Id: I03fac349a946631c20c8e6b49e0ad8934872898e
Reviewed-on: https://gem5-review.googlesource.com/11288
Reviewed-by: Gabe Black <5c8aa1266c03186393d9e7b3b4e3b14239af8201@google.com>
Maintainer: Gabe Black <5c8aa1266c03186393d9e7b3b4e3b14239af8201@google.com>

TUD-OS/gem5-dtu,gem5/gem5,TUD-OS/gem5-dtu,gem5/gem5,gem5/gem5,gem5/gem5,TUD-OS/gem5-dtu,TUD-OS/gem5-dtu,gem5/gem5,TUD-OS/gem5-dtu,TUD-OS/gem5-dtu,TUD-OS/gem5-dtu,gem5/gem5,gem5/gem5