Fix the sbsa-acs-val build: test_p004.c no longer exists
Fix the sbsa-acs-val build: test_p004.c no longer exists

The test_p004.c PCIe test has been removed from the sbsa-acs repo.
Remove it from Makefile.val.

Signed-off-by: Rebecca Cran <0ab09b420c3f4f686e1f6503c93d3111d2038689@nuviainc.com>

ARM-software/arm-enterprise-acs,ARM-software/arm-enterprise-acs,ARM-software/arm-enterprise-acs