fix(bl31): harden check in delegate_async_ea

Following hardening done around ESR_EL3 register usage
 - Panic if exception is anyting other than SError
 - AET bit is only valid if DFSC is 0x11, move DFSC check before AET.

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: Ib15159920f6cad964332fd40f88943aee2bc73b4
1 file changed