feat(brbe): add negative test for ENABLE_BRBE_FOR_NS flag

This test ensures that an EL3 panic occurs when BRBE registers are
accessed when ENABLE_BRBE_FOR_NS=0.

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I3ea7383f9bd2b92e5efe0442f9ad346f95accc44
4 files changed