rockchip: use alternative CID path

Use an alternative path to access the CID of the SD card in MMC0, used
for the generation of MAC addresses. With Kernel 5.10, the device name
of the MMC controller changed, breaking MAC address generation.

The new path is compatible with Kernel 5.4 as well as Kernel 5.10.

Signed-off-by: David Bauer <mail@david-bauer.net>

target/linux/rockchip/armv8/base-files/etc/board.d/02_network

@@ -18,7 +18,7 @@ rockchip_setup_interfaces()
 
 nanopi_r2s_generate_mac()
 {
-	local sd_hash=$(sha256sum /sys/devices/platform/ff500000.dwmmc/mmc_host/mmc0/mmc0:*/cid)
+	local sd_hash=$(sha256sum /sys/class/block/mmcblk0/device/cid)
 	local mac_base=$(macaddr_canonicalize "$(echo "${sd_hash}" | dd bs=1 count=12 2>/dev/null)")
 	echo "$(macaddr_unsetbit_mc "$(macaddr_setbit_la "${mac_base}")")"
 }