raw/skeleton: reset test statistics

raw/skeleton: reset test statistics

Statistics: passed, failed, unsupported and total are kept
in global static variables. As global variables they are initiated
with zeroes. However running test multiple times cumulates results
from previous calls.

This patch resets statistics with zeroes in testsuite_setup().

To reproduce issue fixed by this patch, run rawdev_autotest command
in dpdk-test app multiple times.

Fixes: 55ca1b0f2151 ("raw/skeleton: add test cases")
Cc: stable@dpdk.org
Signed-off-by: Lukasz Wojciechowski <l.wojciechow@partner.samsung.com>
Acked-by: Hemant Agrawal <hemant.agrawal@nxp.com>