db-mv784mp-gp: Rename CONFIG_DB_784MP_GP to CONFIG_TARGET_DB_MV784MP_GP

The value CONFIG_DB_784MP_GP is only used in the DDR code to refer to
CONFIG_TARGET_DB_MV784MP_GP so just use that second value directly.

Cc: Stefan Roese <sr@denx.de>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/ddr/marvell/axp/ddr3_axp_config.h b/drivers/ddr/marvell/axp/ddr3_axp_config.h
index 437a02e..ab09e726 100644
--- a/drivers/ddr/marvell/axp/ddr3_axp_config.h
+++ b/drivers/ddr/marvell/axp/ddr3_axp_config.h
@@ -138,7 +138,7 @@
  * Enables I2C auto detection different options
  */
 #if defined(CONFIG_DB_88F78X60) || defined(CONFIG_DB_88F78X60_REV2) || \
-    defined(CONFIG_DB_784MP_GP)
+    defined(CONFIG_TARGET_DB_MV784MP_GP)
 #define AUTO_DETECTION_SUPPORT
 #endif
 #endif