Unmask SError interrupt and clear SCR_EL3.EA bit ...

This patch disables routing of external aborts from lower exception levels to
EL3 and ensures that a SError interrupt generated as a result of execution in
EL3 is taken locally instead of a lower exception level.

The SError interrupt is enabled in the TSP code only when the operation has not
been directly initiated by the normal world. This is to prevent the possibility
of an asynchronous external abort which originated in normal world from being
taken when execution is in S-EL1.

Fixes ARM-software/tf-issues#153

Change-Id: I157b996c75996d12fd86d27e98bc73dd8bce6cd5

Non-Secure Interrupt support during Standard SMC processing in TSP ...

Implements support for Non Secure Interrupts preempting the
Standard SMC call in EL1. Whenever an IRQ is trapped in the
Secure world we securely handover to the Normal world
to process the interrupt. The normal world then issues
"resume" smc call to resume the previous interrupted SMC call.
Fixes ARM-software/tf-issues#105

Change-Id: I72b760617dee27438754cdfc9fe9bcf4cc024858

Add support for asynchronous FIQ handling in TSP ...

This patch adds support in the TSP to handle FIQ interrupts that are
generated when execution is in the TSP. S-EL1 interrupt are handled
normally and execution resumes at the instruction where the exception
was originally taken. S-EL3 interrupts i.e. any interrupt not
recognized by the TSP are handed to the TSPD. Execution resumes
normally once such an interrupt has been handled at EL3.

Change-Id: Ia3ada9a4fb15670afcc12538a6456f21efe58a8f