hw/misc: Set valid access size for Exynos4210 RNG

The Exynos4210 RNG module requires 32-bit (4-byte) accesses to its registers.
According to the User Manual Section 25.3[1], the registers for RNG operations
are 32-bit. This change ensures that the memory region operations for the
RNG module enforce the correct access sizes, preventing invalid memory accesses.

[1] http://www.mediafire.com/view/8ly2fqls3c9c31c/Exynos_4412_SCP_Users_Manual_Ver.0.10.00_Preliminary0.pdf

Reproducer:
cat << EOF | qemu-system-aarch64 -display none \
-machine accel=qtest, -m 512M -machine smdkc210 -qtest stdio
readb 0x10830454
EOF

Suggested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
Message-id: 20240618163701.3204975-1-zheyuma97@gmail.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/misc/exynos4210_rng.c

@@ -217,6 +217,8 @@ static const MemoryRegionOps exynos4210_rng_ops = {
     .read = exynos4210_rng_read,
     .write = exynos4210_rng_write,
     .endianness = DEVICE_NATIVE_ENDIAN,
+    .valid.min_access_size = 4,
+    .valid.max_access_size = 4,
 };
 
 static void exynos4210_rng_reset(DeviceState *dev)