drivers/virt: add missing linux/interrupt.h to fsl_hypervisor.c

fsl_hypervisor.c calls request_irq() but does not include linux/interrupt.h.
Normally, the driver will compile without error, but it can fail on some
configurations.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>