fix(sdei): return SDEI_EINVAL if signaling state is incorrect

In case a step is omitted when an SDEI event is registered,
enabled, unmasked and then signaled, incorrect code paths
may be reached.

This patch adds additional checks to return early from such
an incorrect state.

Change-Id: Ia2753e9a1b95544e1afa72603574fe830f51ea9f
Signed-off-by: Igor Podgainõi <igor.podgainoi@arm.com>
Signed-off-by: Mark Dykes <mark.dykes@arm.com>
4 files changed