target/arm: Implement HCR.VI and VF

target/arm: Implement HCR.VI and VF

The HCR_EL2 VI and VF bits are supposed to track whether there is
a pending virtual IRQ or virtual FIQ. For QEMU we store the
pending VIRQ/VFIQ status in cs->interrupt_request, so this means:
 * if the register is read we must get these bit values from
   cs->interrupt_request
 * if the register is written then we must write the bit
   values back into cs->interrupt_request

Signed-off-by: Peter Maydell <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
Message-id: 20181012144235[email protected]