build: add -Wnull-dereference to Debug build

This patch adds the `-Wnull-dereference` compile option to Debug
build of RMM. It is added only to Debug build as it shows false
positives for Release build.

Change-Id: Ibf77b679d34c4f62a53296466b5957bd486988e5
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
1 file changed