refactor(context mgmt): remove registers accessible only from secure state from EL2 context

The following registers are only accessible from secure state,
therefore don't need to be saved/restored during world switch.
 - SDER32_EL2
 - VSTCR_EL2
 - VSTTBR_EL2

This patch removes these registers from EL2 context.

Signed-off-by: Zelalem Aweke <zelalem.aweke@arm.com>
Change-Id: I24d08aacb1b6def261c7b37d3e1265bb76adafdc
2 files changed