hw/char/pl011: Restrict MemoryRegionOps implementation access sizes

The pl011_read() and pl011_write() handlers shift the offset
argument by 2, so are implemented on a 32-bit boundary.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230710175102.32429-2-philmd@linaro.org>

hw/char/pl011.c

@@ -358,6 +358,8 @@ static const MemoryRegionOps pl011_ops = {
     .read = pl011_read,
     .write = pl011_write,
     .endianness = DEVICE_NATIVE_ENDIAN,
+    .impl.min_access_size = 4,
+    .impl.max_access_size = 4,
 };
 
 static bool pl011_clock_needed(void *opaque)