msm: Define handle_irq in board-fsm9xxx.c

Recently CONFIG_MULTI_IRQ_HANDLER was enabled by default for
for MSM architectures. FSM based board file didn't define the
interrupt handler, thus FSM kernel failed to handle hardware
interrupts.

Change-Id: I0d2a75fd21bfed14c8ea9bd73d54ab1aab50a645
Acked-by: Kaushik Sikdar <ksikdar@qualcomm.com>
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>