Introduced a build flag 'ENABLE_SYS_REG_TRACE_FOR_NS' to enable trace
system registers access in NS-EL2, or NS-EL1 (when NS-EL2 is
implemented but unused).
Change-Id: Idc1acede4186e101758cbf7bed5af7b634d7d18d
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>