configs: rockchip: rk3308: use CONFIG_DEFAULT_FDT_FILE

all rk3308 boards should use their own dtb file.

also, change fdt_addr_r to avoid following error:
 "ERROR: Did not find a cmdline Flattened Device Tree"
it happens on Radxa ROCK Pi S (256MB/512MB) with kernel built from
Radxa BSP.

Signed-off-by: FUKAUMI Naoki <naoki@radxa.com>
diff --git a/configs/rock-pi-s-rk3308_defconfig b/configs/rock-pi-s-rk3308_defconfig
index bc03171..feb2b2c 100644
--- a/configs/rock-pi-s-rk3308_defconfig
+++ b/configs/rock-pi-s-rk3308_defconfig
@@ -23,6 +23,7 @@
 CONFIG_ANDROID_BOOT_IMAGE=y
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y
+CONFIG_DEFAULT_FDT_FILE="rockchip/rk3308-rock-pi-s.dtb"
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_SPL_MAX_SIZE=0x20000