misc: zynq-xadc: Fix off-by-one

This bounds check was off-by-one. Fix.

Reported-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
Message-id: 1453101737-11255-1-git-send-email-crosthwaite.peter@gmail.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/misc/zynq-xadc.c

@@ -220,7 +220,7 @@ static void zynq_xadc_write(void *opaque, hwaddr offset, uint64_t val,
             break;
         }
 
-        if (xadc_reg > ZYNQ_XADC_NUM_ADC_REGS && xadc_cmd != CMD_NOP) {
+        if (xadc_reg >= ZYNQ_XADC_NUM_ADC_REGS && xadc_cmd != CMD_NOP) {
             qemu_log_mask(LOG_GUEST_ERROR, "read/write op to invalid xadc "
                           "reg 0x%x\n", xadc_reg);
             break;