ARM: BeagleBoard-X15: Enable VTT regulator

BeagleBoard-X15 uses a vtt regulator for DDR3 termination
and this is controlled by gpio7_11. Configuring gpio7_11.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/include/configs/beagle_x15.h b/include/configs/beagle_x15.h
index 8d072c6..c5dde99 100644
--- a/include/configs/beagle_x15.h
+++ b/include/configs/beagle_x15.h
@@ -18,6 +18,8 @@
 #define CONFIG_IODELAY_RECALIBRATION
 #endif
 
+#define CONFIG_BOARD_EARLY_INIT_F
+
 #define CONFIG_NR_DRAM_BANKS		2
 
 #define CONFIG_ENV_SIZE			(64 << 10)