trusty: Add interrupt support

Get list of interrupts from secure mode and register handlers for them.
When an interrupt triggers, disable the interrupt and schedule a work
function. The work functions then masks interrupts at the cpu, reenables
the interrupt and calls into secure mode.

Edge triggered interrupts are not supported.

Change-Id: I731d425e8c946552add6e01cd64dab76337af470
Signed-off-by: Arve Hjønnevåg <arve@android.com>