libseccomp: fix for the ptest result format

The output of libseccomp ptest should follow a unified format as
per this https://wiki.yoctoproject.org/wiki/Ptest



Replaced the test results SUCCESS, FAILURE & SKIPPPED with PASS,
FAIL & SKIP and printing the ptest result with the below format
result: testname

Signed-off-by: Narpat Mali <narpat.mali@windriver.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 30d025a8)
Signed-off-by: Steve Sakoman <steve@sakoman.com>