`requested_irq_received` must be initialized for all tests

requested_irq_received is used to confirm if the CPU is
woken by IRQ, it is set as part of `requested_irq_handler`.
Default it should be cleared for all CPU's under test,
un-intialized value resulted in random failure based on
previous state of variable.

Signed-off-by: Deepika Bhavnani <deepika.bhavnani@arm.com>
Change-Id: Ia3af99a11f3297c2e8fc1ef52e7f18107e2fdfc8