misc: zynq_slcr: Fix MMIO writes

The /4 for offset calculation in MMIO writes was happening twice giving
wrong write offsets. Fix.

While touching the code, change the if-else to be a short returning if
and convert the debug message to a GUEST_ERROR, which is more accurate
for this condition.

Cc: qemu-stable@nongnu.org
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: NPeter Crosthwaite <crosthwaite.peter@gmail.com>
Reviewed-by: NAlistair Francis <alistair.francis@xilinx.com>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/misc/zynq_slcr.c

@@ -393,12 +393,12 @@ static void zynq_slcr_write(void *opaque, hwaddr offset,
         return;
     }
 
-    if (!s->regs[LOCKSTA]) {
-        s->regs[offset / 4] = val;
-    } else {
-        DB_PRINT("SCLR registers are locked. Unlock them first\n");
+    if (s->regs[LOCKSTA]) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "SCLR registers are locked. Unlock them first\n");
         return;
     }
+    s->regs[offset] = val;
 
     switch (offset) {
     case PSS_RST_CTRL: