fix(sdei): set SPSR for SDEI based on TakeException

The SDEI specification now says that during an SDEI
event handler dispatch the SPSR should be set according
to the TakeException() pseudocode function defined in
the Arm Architecture Reference Manual. This patch sets
the SPSR according to the function given in
ARM DDI 0487F.c page J1-7635

Change-Id: Id2f8f2464fd69c701d81626162827e5c4449b658
Signed-off-by: Daniel Boulby <daniel.boulby@arm.com>
3 files changed