Ensure (where possible) that switch statements in services comply with
MISRA rules 16.1 - 16.7.

Change-Id: I47bf6ed4a026201e6fe125ce51842482e99e8bb0
Signed-off-by: Jonathan Wright <jonathan.wright@arm.com>

At present, both SDEI_PRIVATE_RESET and SDEI_SHARED_RESET returns
SDEI_PENDING if they fail to unregister an event. The SDEI specification
however requires that the APIs return SDEI_EDENY in these cases. This
patch fixes the return codes for the reset APIs.

Change-Id: Ic14484c91fa8396910387196c256d1ff13d03afd
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

The SDEI specification requires that binding a client interrupt
dispatches SDEI Normal priority event. This means that dynamic events
can't have Critical priority. Add asserts for this.

Change-Id: I0bdd9e0e642fb2b61810cb9f4cbfbd35bba521d1
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

Change-Id: Iee617a3528225349b6eede2f8abb26da96640678
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

The implementation currently supports only interrupt-based SDEI events,
and supports all interfaces as defined by SDEI specification version
1.0 [1].

Introduce the build option SDEI_SUPPORT to include SDEI dispatcher in
BL31.

Update user guide and porting guide. SDEI documentation to follow.

[1] http://infocenter.arm.com/help/topic/com.arm.doc.den0054a/ARM_DEN0054A_Software_Delegated_Exception_Interface.pdf

Change-Id: I758b733084e4ea3b27ac77d0259705565842241a
Co-authored-by: Yousuf A <yousuf.sait@arm.com>
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>