configs: tbs_a711: lower dram frequency

The dram chip on the tablet was changed. The new one requires a lower
frequency, so change it.

Frequency 564MHz was also stable in the tests, but use slightly lower one
to be on a safe side.

Signed-off-by: Tomas Novotny <tomas@novotny.cz>
[jagan: add MHz in commit message]
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>
diff --git a/configs/tbs_a711_defconfig b/configs/tbs_a711_defconfig
index 253ef5c..007ff89 100644
--- a/configs/tbs_a711_defconfig
+++ b/configs/tbs_a711_defconfig
@@ -3,7 +3,7 @@
 CONFIG_SPL=y
 CONFIG_MACH_SUN8I_A83T=y
 CONFIG_DRAM_TYPE=7
-CONFIG_DRAM_CLK=648
+CONFIG_DRAM_CLK=552
 CONFIG_DRAM_ZQ=15355
 CONFIG_DRAM_ODT_EN=y
 CONFIG_MMC_SUNXI_SLOT_EXTRA=2