rockchip: bob: kevin: Disable dcache in SPL

This causes a hang, so disable it. Unfortunately the RAM-size fix does
not resolve the problem and I am unsure what is wrong. As soon as the
cache is enabled the board appears to hang.

Fixes: 6d8cdfd1536 ("rockchip: spl: Enable caches to speed up checksum validation")

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/chromebook_bob_defconfig b/configs/chromebook_bob_defconfig
index acfe393..b2ecfa6 100644
--- a/configs/chromebook_bob_defconfig
+++ b/configs/chromebook_bob_defconfig
@@ -1,5 +1,6 @@
 CONFIG_ARM=y
 CONFIG_SKIP_LOWLEVEL_INIT=y
+CONFIG_SPL_SYS_DCACHE_OFF=y
 CONFIG_COUNTER_FREQUENCY=24000000
 CONFIG_ARCH_ROCKCHIP=y
 CONFIG_TEXT_BASE=0x00200000