test(realm): validate NS EL1/EL2 context is preserved by RMM

- Test validates that NS EL1/EL2 registers are preserved while
  entering and exiting realm world.
- Test validates that accessing s2por_el1 in realm causes data abort.

Change-Id: I20cbb9d0d59474507f89ee7cf8e127fff4706610
Signed-off-by: Shruti Gupta <shruti.gupta@arm.com>
3 files changed