libseccomp: Add missing files for ptests

pfc files are used e.g. in 38-basic-pfc_coverage.sh
valgrind_test.supp is required, when valgrind is installed, otherwise
all valgrind tests fail

Signed-off-by: Joerg Vehlow <joerg.vehlow@aox.de>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>