benchtests: Expand range of tests names in schema.json

benchtests: Expand range of tests names in schema.json

When executing bench-math the benchmark output is invalid with this
error msg:

    Invalid benchmark output: 'workload-spec2006.wrf' does not match any of
    the regexes: '^[_a-zA-Z0-9]*$¹ or Invalid benchmark output: Additional
    properties are not allowed ('workload-spec2006.wrf' was unexpected)

The error was seen when running the test:
workload-spec2006.wrf, 'stack=1024,guard=1' and 'stack=1024,guard=2'.
The problem is that the current regex's do not accept the hyphen, dot, equal
and comma in the output.

This patch changes the regex in benchout.schema.json to accept symbols in
benchmark tests names.

ChangeLog:

        * benchtests/scripts/benchout.schema.json: Fix regex to accept a
        wider range of tests names.

Signed-off-by: Victor Rodriguez <victor.rodriguez.bahena@intel.com>
Reviewed-By: Siddhesh Poyarekar <siddhesh@sourceware.org>