arm: realm: Add tests for in realm SEA

The RMM/Host could inject Synchronous External Aborts in to the Realm
for various reasons.

RMM injects the SEA for :
  * Instruction/Data fetch from an IPA that is in RIPAS_EMPTY state
  * Instruction fetch from an Unprotected IPA.

Trigger these conditions from within the Realm and verify that the
SEAs are received.

Signed-off-by: Djordje Kovacevic <djordje.kovacevic@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Joey Gouly <joey.gouly@arm.com>