feat(ras): use FEAT_IESB for error synchronization

For synchronization of errors at exception boundries TF-A uses "esb"
instruction with FEAT_RAS or "dsb" and "isb" otherwise. The problem
with esb instruction is, along with synching errors it might also
consume the error, which is not ideal in all scenarios. On the other
hand we can't use dsb always as its in the hot path.

To solve above mentioned problem the best way is to use FEAT_IESB
feature which provides controls to insert an implicit Error
synchronization event at exception entry and exception return.

Assumption in TF-A is, if RAS Extension is present then FEAT_IESB will
also be present and enabled.

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: Ie5861eec5da4028a116406bb4d1fea7dac232456
5 files changed