tcl: improve run-ptest

tcl: improve run-ptest

By setting ERROR_ON_FAILURES we don't need to grep the output to know
if the tests failed.  By default the log runner will print the failed
test case, so we don't need to store the log at all.

Set the skipped tests across multiple lines so that it's easier to see
what skips are related to what bugs, and to avoid very long lines.

Use basename instead of awk to get the test name.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>